{"id":2282,"date":"2026-05-22T13:52:49","date_gmt":"2026-05-22T05:52:49","guid":{"rendered":"http:\/\/www.preluna.xyz\/?p=2282"},"modified":"2026-05-23T16:08:35","modified_gmt":"2026-05-23T08:08:35","slug":"http","status":"publish","type":"post","link":"http:\/\/www.preluna.xyz\/index.php\/2026\/05\/22\/http\/preluna\/text\/","title":{"rendered":"HTTP"},"content":{"rendered":"\n
\"\"<\/div><\/figure>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n

\u7b2c13\u9898<\/h2>\n\n\n\n

\u672c\u9898\u8003\u67e5\u7684\u662f\u201cDNS \u67e5\u8be2 RTT + HTTP\/1.1 \u6d41\u6c34\u7ebf\u8bbf\u95ee\u9875\u9762\u5bf9\u8c61\u201d\u7684\u7efc\u5408\u8ba1\u7b97\u3002<\/p>\n\n\n\n

\u9898\u5e72\u5173\u952e\u4fe1\u606f\u662f\uff1a<\/p>\n\n\n\n

\u4e3b\u673a\u8bbf\u95ee http:\/\/www.cskaoyan.com\/index.html<\/code>\uff0c\u9875\u9762\u4e2d\u8fd8\u5f15\u7528\u4e86\u540c\u4e00\u7f51\u7ad9\u4e0a\u7684 7 \u4e2a\u5c0f\u56fe\u50cf\u6587\u4ef6\u3002\u6d4f\u89c8\u5668\u4f7f\u7528\u6d41\u6c34\u7ebf\u65b9\u5f0f\u7684 HTTP\/1.1\u3002\u4e3b\u673a\u5230\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u3001\u5404\u57df\u540d\u670d\u52a1\u5668\u4e4b\u95f4\u7684\u5f80\u8fd4\u65f6\u5ef6\u90fd\u4e3a 1RTT\u3002\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u63d0\u4f9b\u9012\u5f52\u67e5\u8be2\uff0c\u5176\u4ed6\u57df\u540d\u670d\u52a1\u5668\u63d0\u4f9b\u8fed\u4ee3\u67e5\u8be2\u3002<\/p>\n\n\n\n

\u5148\u7b97 DNS \u89e3\u6790\u3002\u6700\u574f\u60c5\u51b5\u4e0b\u6ca1\u6709\u7f13\u5b58\uff0c\u9700\u8981\uff1a<\/p>\n\n\n\n

\u4e3b\u673a \u2192 \u672c\u5730\u57df\u540d\u670d\u52a1\u5668\uff1a1RTT\n\u672c\u5730\u57df\u540d\u670d\u52a1\u5668 \u2192 \u6839\u57df\u540d\u670d\u52a1\u5668\uff1a1RTT\n\u672c\u5730\u57df\u540d\u670d\u52a1\u5668 \u2192 .com \u9876\u7ea7\u57df\u540d\u670d\u52a1\u5668\uff1a1RTT\n\u672c\u5730\u57df\u540d\u670d\u52a1\u5668 \u2192 cskaoyan.com \u6743\u5a01\u57df\u540d\u670d\u52a1\u5668\uff1a1RTT\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5 DNS \u89e3\u6790\u6700\u591a\u9700\u8981\uff1a<\/p>\n\n\n\n
4RTT\n<\/code><\/pre>\n\n\n\n
\u518d\u7b97 HTTP \u8bbf\u95ee\u8fc7\u7a0b\u3002\u89e3\u6790\u51fa IP \u540e\uff0c\u9700\u8981\u5148\u5efa\u7acb TCP \u8fde\u63a5\uff1a<\/p>\n\n\n\n
TCP \u4e09\u6b21\u63e1\u624b\uff1a1RTT\n\u8bf7\u6c42\u5e76\u63a5\u6536 index.html\uff1a1RTT\n\u8bf7\u6c42\u5e76\u63a5\u6536 7 \u4e2a\u5c0f\u56fe\u50cf\u6587\u4ef6\uff1a1RTT\n<\/code><\/pre>\n\n\n\n
\u6ce8\u610f\u8fd9\u91cc\u662f HTTP\/1.1 \u6d41\u6c34\u7ebf\u65b9\u5f0f\uff0c\u540c\u4e00 TCP \u8fde\u63a5\u4e0a\u53ef\u4ee5\u8fde\u7eed\u53d1\u9001\u591a\u4e2a\u8bf7\u6c42\uff0c\u4e0d\u9700\u8981\u6bcf\u4e2a\u56fe\u7247\u90fd\u5355\u72ec\u7b49 1RTT\u3002\u6240\u4ee5 7 \u4e2a\u5c0f\u56fe\u50cf\u6587\u4ef6\u4e0d\u662f 7RTT\uff0c\u800c\u662f\u53ef\u4ee5\u6309 1RTT \u5904\u7406\u3002<\/p>\n\n\n\n
\u603b\u65f6\u95f4\u4e3a\uff1a<\/p>\n\n\n\n
DNS \u89e3\u6790 4RTT + TCP \u5efa\u8fde 1RTT + \u83b7\u53d6\u4e3b\u9875 1RTT + \u83b7\u53d6 7 \u4e2a\u56fe\u7247 1RTT = 7RTT\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u7b2c13\u9898\u9009 C\uff0c7\u3002<\/p>\n\n\n\n
\u6613\u9519\u70b9\u5728\u4e8e\u628a 7 \u4e2a\u56fe\u7247\u8bef\u7b97\u6210 7 \u4e2a RTT\u3002\u6d41\u6c34\u7ebf HTTP\/1.1 \u7684\u5173\u952e\u5c31\u662f\u591a\u4e2a\u8bf7\u6c42\u53ef\u4ee5\u8fde\u7eed\u53d1\u51fa\uff0c\u4e0d\u5fc5\u7b49\u524d\u4e00\u4e2a\u54cd\u5e94\u56de\u6765\u540e\u518d\u53d1\u4e0b\u4e00\u4e2a\u8bf7\u6c42\u3002<\/p>\n\n\n\n
\u4f60\u8fd9\u4e2a\u8d28\u7591\u662f\u5bf9\u7684\uff1a\u7b2c14\u9898\u6211\u4e4b\u524d\u7684\u89e3\u91ca\u6ca1\u6709\u5c55\u5f00\u201c\u62e5\u585e\u7a97\u53e3\/\u53d1\u9001\u7a97\u53e3\u53d8\u5316\u201d\uff0c\u6240\u4ee5\u63a8\u7406\u4e0d\u591f\u4e25\u8c28\uff1b\u53ea\u662f\u6700\u540e\u7684 4RTT + 2MSL<\/code> \u6070\u597d\u548c\u5b98\u65b9\u7b54\u6848\u4e00\u81f4\u3002\u7b2c15\u9898\u6211\u4e4b\u524d\u6309\u201c\u5185\u7f51\u4e3b\u673a\u65b0\u53d1\u8d77\u4e00\u4e2a\u8fde\u63a5\u201d\u7406\u89e3\u4e86\uff0c\u4f46\u8fd9\u9053\u9898\u7684\u5b98\u65b9\u8003\u70b9\u662f\u201c\u6e90\u7aef\u53e3 80 \u8868\u793a HTTP \u54cd\u5e94\u5206\u7ec4\uff0c\u54cd\u5e94\u5206\u7ec4\u5fc5\u987b\u5339\u914d\u5df2\u6709 NAT \u8868\u9879\u201d\uff0c\u6240\u4ee5\u6309\u8003\u7814\u9898\u610f\u5e94\u9009 C\u3002<\/h2>\n\n\n\n
\u7b2c14\u9898\uff1a\u4e3a\u4ec0\u4e48\u5fc5\u987b\u8003\u8651\u62e5\u585e\u7a97\u53e3\uff0c\u4f46\u6211\u6ca1\u8003\u8651\u4e5f\u5f97\u5230\u540c\u6837\u7b54\u6848\uff1f<\/h2>\n\n\n\n
\u672c\u9898\u7684\u5173\u952e\u4e0d\u662f\u5355\u7eaf\u7684\u201c\u56db\u6b21\u6325\u624b\u9700\u8981 2RTT\u201d\uff0c\u800c\u662f\uff1a\u670d\u52a1\u5668 S \u8fd8\u6709 4KB \u6570\u636e\u6ca1\u53d1\u5b8c\uff0c\u5e76\u4e14\u521d\u59cb\u62e5\u585e\u7a97\u53e3\u53ea\u6709 1MSS = 1KB<\/code>\uff0c\u56e0\u6b64\u6570\u636e\u4e0d\u80fd\u4e00\u6b21\u6027\u5168\u53d1\u51fa\u53bb\u3002<\/p>\n\n\n\n
\u9898\u5e72\u6761\u4ef6\u662f\uff1a<\/p>\n\n\n\n
RTT = 50ms\nMSL = 800ms\nMSS = 1KB\nHTTP \u54cd\u5e94\u6570\u636e = 5KB\n\u521d\u59cb\u62e5\u585e\u7a97\u53e3 = 1MSS = 1KB\nH \u6536\u5230\u7b2c\u4e00\u4e2a 1KB \u540e\uff0c\u5c31\u5411 S \u53d1\u9001 FIN\n<\/code><\/pre>\n\n\n\n
\u5b98\u65b9\u7684\u6b63\u786e\u8fc7\u7a0b\u53ef\u4ee5\u8fd9\u6837\u770b\uff1a<\/p>\n\n\n\n
t = 0\nH \u2192 S\uff1aSYN\n\nt = 1RTT\nH \u6536\u5230 SYN+ACK\uff0c\u7136\u540e\u53d1\u9001\u7b2c 3 \u6b21\u63e1\u624b ACK\n\u8fd9\u4e2a ACK \u4e2d\u987a\u4fbf\u643a\u5e26 HTTP \u8bf7\u6c42\n\nt = 2RTT\nH \u6536\u5230 S \u53d1\u6765\u7684\u7b2c 1KB \u6570\u636e\n\u56e0\u4e3a\u521d\u59cb\u62e5\u585e\u7a97\u53e3\u53ea\u6709 1KB\uff0c\u6240\u4ee5 S \u4e00\u5f00\u59cb\u53ea\u80fd\u53d1 1KB\nH \u6536\u5230\u540e\uff0c\u5411 S \u53d1\u9001 ACK + FIN\n\nt = 2.5RTT\nS \u6536\u5230 H \u7684 ACK + FIN\n\u6b64\u65f6 ACK \u786e\u8ba4\u4e86\u524d 1KB \u6570\u636e\uff0c\u62e5\u585e\u7a97\u53e3\u589e\u5927\u5230 2KB\nS \u8fd8\u6709 4KB \u6ca1\u53d1\uff0c\u4e8e\u662f\u5148\u53d1\u9001 2KB\n\nt = 3RTT\nH \u6536\u5230\u8fd9 2KB\uff0c\u5411 S \u53d1\u9001 ACK\n\nt = 3.5RTT\nS \u6536\u5230 ACK\uff0c\u518d\u53d1\u9001\u6700\u540e 2KB\uff0c\u5e76\u5728\u6700\u540e\u4e00\u4e2a\u62a5\u6587\u6bb5\u4e2d\u643a\u5e26 FIN\n\nt = 4RTT\nH \u6536\u5230\u6700\u540e 2KB + FIN\uff0c\u5411 S \u53d1\u9001 ACK\nH \u8fdb\u5165 TIME-WAIT\uff0c\u7b49\u5f85 2MSL\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u603b\u65f6\u95f4\u662f\uff1a<\/p>\n\n\n\n
4RTT + 2MSL\n= 4 \u00d7 50ms + 2 \u00d7 800ms\n= 200ms + 1600ms\n= 1800ms\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u7b2c14\u9898\u9009 D\u3002<\/p>\n\n\n\n
\u6211\u4e4b\u524d\u7684\u8bf4\u6cd5\u628a\u8fc7\u7a0b\u7c97\u7565\u5199\u6210\uff1a<\/p>\n\n\n\n
\u4e09\u6b21\u63e1\u624b 1RTT\n\u8bf7\u6c42\u5e76\u6536\u5230\u7b2c\u4e00\u4e2a\u6570\u636e 1RTT\n\u8fde\u63a5\u91ca\u653e 2RTT\nTIME-WAIT 2MSL\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a\u5206\u89e3\u6700\u540e\u4e5f\u662f\uff1a<\/p>\n\n\n\n
4RTT + 2MSL\n<\/code><\/pre>\n\n\n\n
\u4f46\u5b83\u7684\u95ee\u9898\u5728\u4e8e\uff1a\u6211\u6ca1\u6709\u8bf4\u660e\u5269\u4f59 4KB \u6570\u636e\u4e3a\u4ec0\u4e48\u6b63\u597d\u53c8\u5360\u7528\u4e86 2RTT\u3002\u5b98\u65b9\u771f\u6b63\u7684\u4f9d\u636e\u662f\u62e5\u585e\u7a97\u53e3\u53d8\u5316\uff1a<\/p>\n\n\n\n
\u521d\u59cb cwnd = 1KB\uff0c\u6240\u4ee5\u7b2c\u4e00\u6b21\u53ea\u80fd\u53d1 1KB\n\u6536\u5230 ACK \u540e cwnd = 2KB\uff0c\u6240\u4ee5\u7b2c\u4e8c\u6279\u53d1 2KB\n\u518d\u6536\u5230 ACK \u540e\uff0c\u6700\u540e 2KB \u548c FIN \u4e00\u8d77\u53d1\u51fa\n<\/code><\/pre>\n\n\n\n
\u4e5f\u5c31\u662f\u8bf4\uff0c\u6211\u4e4b\u524d\u628a\u201c\u5269\u4f59\u6570\u636e\u53d1\u9001 + FIN \u91ca\u653e\u201d\u7c97\u7565\u538b\u6210\u4e86\u201c\u91ca\u653e\u8fc7\u7a0b 2RTT\u201d\uff0c\u6570\u503c\u4e0a\u649e\u5bf9\u4e86\uff0c\u4f46\u4e25\u683c\u8003\u7814\u89e3\u9898\u5fc5\u987b\u6309\u5b98\u65b9\u8fd9\u79cd\u7a97\u53e3\u53d8\u5316\u6765\u7b97\u3002\u5426\u5219\u6362\u4e00\u7ec4\u7a97\u53e3\u5927\u5c0f\uff0c\u7b80\u5316\u7b97\u6cd5\u5c31\u53ef\u80fd\u9519\u3002<\/p>\n\n\n\n
\u7b2c15\u9898\uff1a\u600e\u4e48\u5224\u65ad 192.168.32.56 \u662f\u79c1\u6709\u5730\u5740\uff1f<\/h2>\n\n\n\n
IPv4 \u79c1\u6709\u5730\u5740\u8303\u56f4\u5728\u8003\u7814\u4e2d\u8981\u76f4\u63a5\u8bb0\u4f4f\uff1a<\/p>\n\n\n\n
10.0.0.0 ~ 10.255.255.255        \u5373 10.0.0.0\/8\n172.16.0.0 ~ 172.31.255.255      \u5373 172.16.0.0\/12\n192.168.0.0 ~ 192.168.255.255    \u5373 192.168.0.0\/16\n<\/code><\/pre>\n\n\n\n
\u9898\u76ee\u4e2d\u7684\u5730\u5740\u662f\uff1a<\/p>\n\n\n\n
192.168.32.56\n<\/code><\/pre>\n\n\n\n
\u5b83\u843d\u5728\uff1a<\/p>\n\n\n\n
192.168.0.0\/16\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u5b83\u662f\u79c1\u6709\u5730\u5740\u3002<\/p>\n\n\n\n
NAT \u8def\u7531\u5668\u7684\u516c\u7f51\u5730\u5740\u662f\uff1a<\/p>\n\n\n\n
205.56.79.35\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a\u4e0d\u5728\u4e0a\u9762\u4e09\u4e2a\u79c1\u6709\u5730\u5740\u8303\u56f4\u5185\uff0c\u6240\u4ee5\u662f\u516c\u7f51\u5730\u5740\u3002<\/p>\n\n\n\n
\u7b2c15\u9898\uff1a\u4e3a\u4ec0\u4e48\u6e90\u7aef\u53e3 80 \u8868\u793a HTTP \u54cd\u5e94\u5206\u7ec4\uff1f<\/h2>\n\n\n\n
HTTP \u4f7f\u7528 TCP 80 \u7aef\u53e3\u65f6\uff0c\u901a\u5e38\u6709\u8fd9\u6837\u7684\u65b9\u5411\u5173\u7cfb\uff1a<\/p>\n\n\n\n
HTTP \u8bf7\u6c42\uff1a\n\u5ba2\u6237\u7aef\u968f\u673a\u7aef\u53e3 \u2192 Web \u670d\u52a1\u5668 80 \u7aef\u53e3\n\nHTTP \u54cd\u5e94\uff1a\nWeb \u670d\u52a1\u5668 80 \u7aef\u53e3 \u2192 \u5ba2\u6237\u7aef\u968f\u673a\u7aef\u53e3\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u5224\u65ad HTTP \u62a5\u6587\u65b9\u5411\u65f6\uff0c\u8981\u770b 80 \u7aef\u53e3\u51fa\u73b0\u5728\u6e90\u7aef\u53e3\u8fd8\u662f\u76ee\u7684\u7aef\u53e3\u3002<\/p>\n\n\n\n
\u5982\u679c\u662f\uff1a<\/p>\n\n\n\n
\u6e90\u7aef\u53e3 = 80\n<\/code><\/pre>\n\n\n\n
\u901a\u5e38\u8bf4\u660e\u8fd9\u4e2a\u62a5\u6587\u662f Web \u670d\u52a1\u5668\u53d1\u51fa\u7684\u54cd\u5e94\u62a5\u6587\u3002<\/p>\n\n\n\n
\u5982\u679c\u662f\uff1a<\/p>\n\n\n\n
\u76ee\u7684\u7aef\u53e3 = 80\n<\/code><\/pre>\n\n\n\n
\u901a\u5e38\u8bf4\u660e\u8fd9\u4e2a\u62a5\u6587\u662f\u5ba2\u6237\u7aef\u53d1\u7ed9 Web \u670d\u52a1\u5668\u7684\u8bf7\u6c42\u62a5\u6587\u3002<\/p>\n\n\n\n
\u672c\u9898\u7ed9\u7684\u662f\uff1a<\/p>\n\n\n\n
\u6e90 IP \u5730\u5740\uff1a192.168.32.56\n\u6e90\u7aef\u53e3\uff1a80\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u6309\u8003\u7814\u9898\u610f\uff0c\u5b83\u8868\u793a\uff1a<\/p>\n\n\n\n
\u5185\u7f51\u4e3b\u673a 192.168.32.56 \u4f5c\u4e3a Web \u670d\u52a1\u5668\uff0c\u6b63\u5728\u53d1\u51fa HTTP \u54cd\u5e94\u5206\u7ec4\u3002\n<\/code><\/pre>\n\n\n\n
\u7b2c15\u9898\uff1a\u4e3a\u4ec0\u4e48\u4e0d\u662f\u201c\u65b0\u589e\u4e00\u4e2a NAT \u8868\u9879\u201d\uff1f<\/h2>\n\n\n\n
NAT \u8868\u4e2d\u5df2\u6709\u8868\u9879\u662f\uff1a<\/p>\n\n\n\n
2056  \u2194  192.168.32.56:21\n2057  \u2194  192.168.32.56:20\n1892  \u2194  192.168.48.26:80\n2256  \u2194  192.168.55.106:80\n<\/code><\/pre>\n\n\n\n
\u73b0\u5728\u6536\u5230\u7684\u5206\u7ec4\u6765\u81ea\uff1a<\/p>\n\n\n\n
192.168.32.56:80\n<\/code><\/pre>\n\n\n\n
\u8868\u4e2d\u6ca1\u6709\u8fd9\u4e2a\u6620\u5c04\u3002<\/p>\n\n\n\n
\u6ce8\u610f\uff0c\u4e0d\u80fd\u53ea\u770b IP \u5730\u5740\u76f8\u540c\u3002NAT\/PAT \u8f6c\u6362\u8981\u770b\u7684\u662f\uff1a<\/p>\n\n\n\n
\u5185\u90e8 IP \u5730\u5740 + \u5185\u90e8\u7aef\u53e3\u53f7\n<\/code><\/pre>\n\n\n\n
\u8868\u4e2d\u867d\u7136\u6709\uff1a<\/p>\n\n\n\n
192.168.32.56:21\n192.168.32.56:20\n<\/code><\/pre>\n\n\n\n
\u4f46\u6ca1\u6709\uff1a<\/p>\n\n\n\n
192.168.32.56:80\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u5b83\u4e0d\u5339\u914d\u5df2\u6709 NAT \u8868\u9879\u3002<\/p>\n\n\n\n
\u5982\u679c\u8fd9\u4e2a\u62a5\u6587\u771f\u7684\u662f\u53d1\u7ed9\u5916\u7f51\u4e3b\u673a\u7684 HTTP \u54cd\u5e94\uff0c\u90a3\u4e48\u524d\u63d0\u662f\u5916\u7f51\u4e3b\u673a\u66fe\u7ecf\u5411\u5185\u7f51 Web \u670d\u52a1\u5668 192.168.32.56:80<\/code> \u53d1\u8fc7 HTTP \u8bf7\u6c42\u3002<\/p>\n\n\n\n
\u4f46\u662f\u5916\u7f51\u4e3b\u673a\u4e0d\u80fd\u76f4\u63a5\u8bbf\u95ee\u79c1\u6709\u5730\u5740 192.168.32.56<\/code>\u3002\u5b83\u5fc5\u987b\u8bbf\u95ee NAT \u8def\u7531\u5668\u7684\u516c\u7f51\u5730\u5740\uff0c\u518d\u7531 NAT \u8def\u7531\u5668\u6839\u636e\u8868\u9879\u8f6c\u53d1\u5230\u5185\u7f51\u670d\u52a1\u5668\u3002\u56e0\u6b64\uff0c\u82e5\u5916\u7f51\u8bf7\u6c42\u771f\u7684\u80fd\u5230\u8fbe 192.168.32.56:80<\/code>\uff0cNAT \u8868\u4e2d\u5fc5\u7136\u5e94\u8be5\u5b58\u5728\u7c7b\u4f3c\uff1a<\/p>\n\n\n\n
\u67d0\u4e2a\u8f6c\u6362\u7aef\u53e3 \u2194 192.168.32.56:80\n<\/code><\/pre>\n\n\n\n
\u53ef\u662f\u73b0\u5728\u8868\u4e2d\u6ca1\u6709\u8fd9\u4e00\u9879\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u8fd9\u4e2a HTTP \u54cd\u5e94\u5206\u7ec4\u4e0d\u53ef\u80fd\u662f\u5bf9\u5916\u7f51\u4e3b\u673a\u5408\u6cd5\u8bf7\u6c42\u7684\u54cd\u5e94\u3002<\/p>\n\n\n\n
\u7b2c15\u9898\uff1a\u5b98\u65b9\u8bf4\u201c\u53ea\u53ef\u80fd\u662f\u5bf9\u5185\u7f51\u4e3b\u673a\u8bf7\u6c42\u7684\u54cd\u5e94\u201d\u600e\u4e48\u7406\u89e3\uff1f<\/h2>\n\n\n\n
\u5b98\u65b9\u7684\u610f\u601d\u662f\uff1a<\/p>\n\n\n\n
\u8fd9\u4e2a\u5206\u7ec4\u6e90\u5730\u5740\u662f\u79c1\u6709\u5730\u5740\uff0c\u6e90\u7aef\u53e3\u662f 80\uff0c\u8bf4\u660e\u5b83\u50cf\u662f\u5185\u7f51 Web \u670d\u52a1\u5668\u53d1\u51fa\u7684 HTTP \u54cd\u5e94\u3002\u65e2\u7136 NAT \u8868\u4e2d\u6ca1\u6709 192.168.32.56:80<\/code> \u7684\u8f6c\u6362\u9879\uff0c\u90a3\u4e48\u5b83\u4e0d\u53ef\u80fd\u662f\u5728\u54cd\u5e94\u5916\u7f51\u4e3b\u673a\u901a\u8fc7 NAT \u53d1\u6765\u7684\u8bf7\u6c42\u3002<\/p>\n\n\n\n
\u90a3\u5b83\u66f4\u53ef\u80fd\u662f\u5728\u54cd\u5e94\u53e6\u4e00\u4e2a\u5185\u7f51\u4e3b\u673a\u7684 HTTP \u8bf7\u6c42\u3002<\/p>\n\n\n\n
\u4f8b\u5982\uff1a<\/p>\n\n\n\n
\u5185\u7f51\u4e3b\u673a A\uff1a192.168.32.56:80\n\u5185\u7f51\u4e3b\u673a B\uff1a192.168.x.x:\u968f\u673a\u7aef\u53e3\n<\/code><\/pre>\n\n\n\n
B \u8bf7\u6c42 A \u7684 Web \u670d\u52a1\uff0cA \u8fd4\u56de HTTP \u54cd\u5e94\u3002\u8fd9\u79cd\u901a\u4fe1\u672c\u6765\u5c31\u5728\u5185\u7f51\u4e2d\u5b8c\u6210\uff0c\u4e0d\u9700\u8981 NAT \u8def\u7531\u5668\u628a\u5b83\u8f6c\u53d1\u5230\u516c\u7f51\u3002<\/p>\n\n\n\n
\u56e0\u6b64 NAT \u8def\u7531\u5668\u770b\u5230\u8fd9\u4e2a\u6ca1\u6709\u5339\u914d\u8868\u9879\u7684\u5206\u7ec4\u65f6\uff0c\u4e0d\u5e94\u8be5\u65b0\u589e NAT \u8f6c\u6362\u9879\uff0c\u4e5f\u4e0d\u5e94\u8be5\u8f6c\u53d1\u5230\u516c\u7f51\uff0c\u800c\u662f\u4e22\u5f03\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u7b2c15\u9898\u9009 C\u3002<\/p>\n\n\n\n
\u7b2c15\u9898\u7684\u5feb\u901f\u5224\u65ad\u53e3\u8bc0<\/h2>\n\n\n\n
\u8fd9\u7c7b NAT \u9898\u53ef\u4ee5\u6309\u8fd9\u4e2a\u987a\u5e8f\u5224\u65ad\uff1a<\/p>\n\n\n\n
\u7b2c\u4e00\u6b65\uff1a\u770b\u5730\u5740\u662f\u4e0d\u662f\u79c1\u6709\u5730\u5740\n192.168.x.x\u300110.x.x.x\u3001172.16~31.x.x \u90fd\u662f\u79c1\u6709\u5730\u5740\n\n\u7b2c\u4e8c\u6b65\uff1a\u770b\u7aef\u53e3 80 \u5728\u6e90\u7aef\u53e3\u8fd8\u662f\u76ee\u7684\u7aef\u53e3\n\u76ee\u7684\u7aef\u53e3 80\uff1a\u901a\u5e38\u662f HTTP \u8bf7\u6c42\n\u6e90\u7aef\u53e3 80\uff1a\u901a\u5e38\u662f HTTP \u54cd\u5e94\n\n\u7b2c\u4e09\u6b65\uff1a\u67e5 NAT \u8868\u662f\u5426\u6709 \u201c\u5185\u90e8 IP + \u5185\u90e8\u7aef\u53e3\u201d \u5bf9\u5e94\u9879\n\u6709\u8868\u9879\uff1a\u6309\u8868\u9879\u8f6c\u6362\n\u65e0\u8868\u9879\uff1a\n    \u5982\u679c\u662f\u5185\u7f51\u4e3b\u673a\u65b0\u53d1\u8d77\u7684\u8bf7\u6c42\uff0c\u53ef\u4ee5\u65b0\u589e\u8868\u9879\n    \u5982\u679c\u662f\u54cd\u5e94\u5206\u7ec4\uff0c\u5219\u4e0d\u80fd\u51ed\u7a7a\u65b0\u589e\u8868\u9879\uff0c\u5e94\u4e22\u5f03\n<\/code><\/pre>\n\n\n\n
\u672c\u9898\u662f\uff1a<\/p>\n\n\n\n
192.168.32.56 \u662f\u79c1\u6709\u5730\u5740\n\u6e90\u7aef\u53e3 80\uff0c\u8bf4\u660e\u662f HTTP \u54cd\u5e94\nNAT \u8868\u4e2d\u6ca1\u6709 192.168.32.56:80\n\u6240\u4ee5\u4e22\u5f03\n<\/code><\/pre>\n\n\n\n
\u56e0\u6b64\u7b2c15\u9898\u6309\u5b98\u65b9\u7b54\u6848\u9009 C\u3002<\/p>\n\n\n\n
\u7b2c16\u9898<\/h2>\n\n\n\n
\u672c\u9898\u95ee\u201c\u4f7f\u7528\u6d4f\u89c8\u5668\u8bbf\u95ee\u67d0\u5927\u5b66\u7684 Web \u7f51\u7ad9\u4e3b\u9875\u65f6\uff0c\u4e0d\u53ef\u80fd\u4f7f\u7528\u5230\u7684\u534f\u8bae\u201d\u3002<\/p>\n\n\n\n
\u9009\u9879\u662f\uff1a<\/p>\n\n\n\n
A. PPP\nB. ARP\nC. UDP\nD. SMTP\n<\/code><\/pre>\n\n\n\n
\u6d4f\u89c8 Web \u4e3b\u9875\u65f6\uff0c\u4e3b\u8981\u6d89\u53ca\uff1a<\/p>\n\n\n\n
\u5e94\u7528\u5c42\uff1aHTTP\n\u4f20\u8f93\u5c42\uff1aTCP\n\u7f51\u7edc\u5c42\uff1aIP\n\u6570\u636e\u94fe\u8def\u5c42\uff1a\u53ef\u80fd\u7528\u4ee5\u592a\u7f51\u3001PPP \u7b49\n<\/code><\/pre>\n\n\n\n
\u6b64\u5916\uff0c\u8bbf\u95ee\u57df\u540d\u65f6\u9700\u8981 DNS\uff0c\u800c DNS \u901a\u5e38\u4f7f\u7528 UDP\uff0c\u6240\u4ee5 UDP \u53ef\u80fd\u88ab\u7528\u5230\u3002\u82e5\u4e3b\u673a\u5728\u5c40\u57df\u7f51\u4e2d\u8bbf\u95ee\u7f51\u5173\uff0c\u8fd8\u53ef\u80fd\u7528 ARP \u83b7\u53d6\u7f51\u5173\u7684 MAC \u5730\u5740\u3002PPP \u4e5f\u53ef\u80fd\u7528\u4e8e\u67d0\u4e9b\u63a5\u5165\u94fe\u8def\u3002<\/p>\n\n\n\n
SMTP \u662f Simple Mail Transfer Protocol\uff0c\u7b80\u5355\u90ae\u4ef6\u4f20\u8f93\u534f\u8bae\uff0c\u7528\u4e8e\u7535\u5b50\u90ae\u4ef6\u4f20\u8f93\uff0c\u4e0d\u7528\u4e8e\u6d4f\u89c8\u5668\u8bbf\u95ee Web \u4e3b\u9875\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u7b2c16\u9898\u9009 D\uff0cSMTP\u3002<\/p>\n\n\n\n
\u8fd9\u9898\u7684\u9677\u9631\u662f\u4e0d\u8981\u53ea\u76ef\u7740 HTTP\u3002\u8bbf\u95ee\u7f51\u9875\u867d\u7136\u5e94\u7528\u5c42\u662f HTTP\uff0c\u4f46\u6574\u4e2a\u901a\u4fe1\u8fc7\u7a0b\u4e2d\u53ef\u80fd\u4f1a\u6d89\u53ca ARP\u3001DNS\/UDP\u3001PPP \u7b49\u5176\u4ed6\u5c42\u6b21\u7684\u534f\u8bae\u3002<\/p>\n\n\n\n
\u7b2c17\u9898<\/h2>\n\n\n\n
HTTP \u8bf7\u6c42\u62a5\u6587\u4e3a\uff1a<\/p>\n\n\n\n
GET \/index.html HTTP\/1.1\nHost: www.test.edu.cn\nConnection: Close\nCookie: 123456\n<\/code><\/pre>\n\n\n\n
\u9010\u9879\u5206\u6790\u3002<\/p>\n\n\n\n
A \u8bf4\u201c\u8be5\u6d4f\u89c8\u5668\u8bf7\u6c42\u6d4f\u89c8 index.html\u201d\u3002\u8fd9\u662f\u6b63\u786e\u7684\u3002GET \/index.html HTTP\/1.1<\/code> \u8868\u793a\u8bf7\u6c42\u670d\u52a1\u5668\u4e0a\u7684 \/index.html<\/code> \u8d44\u6e90\u3002<\/p>\n\n\n\n
B \u8bf4\u201cindex.html \u5b58\u653e\u5728 www.test.edu.cn<\/a> \u4e0a\u201d\u3002\u4ece\u8003\u8bd5\u8bed\u5883\u770b\uff0cHost: www.test.edu.cn<\/code> \u8868\u793a\u8bf7\u6c42\u7684\u76ee\u6807\u4e3b\u673a\u662f www.test.edu.cn<\/code>\uff0c\u6240\u4ee5\u53ef\u4ee5\u8ba4\u4e3a\u8be5\u8d44\u6e90\u662f\u5411\u8fd9\u4e2a\u4e3b\u673a\u8bf7\u6c42\u7684\u3002\u4e25\u683c\u8bf4\uff0c\u8bf7\u6c42\u62a5\u6587\u4e0d\u80fd\u4fdd\u8bc1\u8d44\u6e90\u4e00\u5b9a\u5b58\u5728\uff0c\u670d\u52a1\u5668\u4e5f\u53ef\u80fd\u8fd4\u56de 404\uff0c\u4f46\u672c\u9898\u4e0d\u662f\u8003\u8fd9\u4e2a\u7ec6\u8282\u3002<\/p>\n\n\n\n
C \u8bf4\u201c\u8be5\u6d4f\u89c8\u5668\u8bf7\u6c42\u4f7f\u7528\u6301\u7eed\u8fde\u63a5\u201d\u3002\u8fd9\u662f\u9519\u8bef\u7684\u3002HTTP\/1.1 \u9ed8\u8ba4\u652f\u6301\u6301\u7eed\u8fde\u63a5\uff0c\u4f46\u8fd9\u91cc\u8bf7\u6c42\u5934\u660e\u786e\u5199\u4e86\uff1a<\/p>\n\n\n\n
Connection: Close\n<\/code><\/pre>\n\n\n\n
\u8fd9\u8868\u793a\u5ba2\u6237\u7aef\u5e0c\u671b\u670d\u52a1\u5668\u54cd\u5e94\u540e\u5173\u95ed TCP \u8fde\u63a5\uff0c\u4e0d\u4f7f\u7528\u6301\u7eed\u8fde\u63a5\u3002<\/p>\n\n\n\n
D \u8bf4\u201c\u8be5\u6d4f\u89c8\u5668\u66fe\u7ecf\u6d4f\u89c8\u8fc7 www.test.edu.cn\u201d\u3002\u8fd9\u662f\u6b63\u786e\u7684\u3002\u8bf7\u6c42\u4e2d\u5e26\u6709\uff1a<\/a><\/p>\n\n\n\n
Cookie: 123456\n<\/code><\/pre>\n\n\n\n
Cookie \u901a\u5e38\u662f\u670d\u52a1\u5668\u6b64\u524d\u901a\u8fc7 Set-Cookie<\/code> \u8bbe\u7f6e\u5230\u6d4f\u89c8\u5668\u4e2d\u7684\uff0c\u6d4f\u89c8\u5668\u4e4b\u540e\u518d\u6b21\u8bbf\u95ee\u8be5\u7ad9\u70b9\u65f6\u4f1a\u643a\u5e26 Cookie\u3002\u56e0\u6b64\u53ef\u4ee5\u5224\u65ad\u8be5\u6d4f\u89c8\u5668\u4e4b\u524d\u8bbf\u95ee\u8fc7\u8be5\u7ad9\u70b9\uff0c\u6216\u8005\u81f3\u5c11\u4e4b\u524d\u83b7\u5f97\u8fc7\u8be5\u7ad9\u70b9\u76f8\u5173 Cookie\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u7b2c17\u9898\u9009 C\u3002<\/p>\n\n\n\n
\u8fd9\u9898\u6700\u5e38\u89c1\u7684\u8bef\u533a\u662f\u770b\u5230 HTTP\/1.1<\/code> \u5c31\u76f4\u63a5\u8ba4\u4e3a\u4e00\u5b9a\u662f\u6301\u7eed\u8fde\u63a5\u3002HTTP\/1.1 \u9ed8\u8ba4\u6301\u7eed\u8fde\u63a5\uff0c\u4f46 Connection: Close<\/code> \u4f1a\u660e\u786e\u8981\u6c42\u5173\u95ed\u8fde\u63a5\u3002<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u672c\u9898\u7ed3\u8bba\u5982\u4e0b\uff1a<\/p>\n\n\n\n
1\uff09Web \u670d\u52a1\u5668\u7684 IP \u5730\u5740\u662f 64.170.98.32<\/code>\u3002
\u8be5\u4e3b\u673a\u9ed8\u8ba4\u7f51\u5173\u7684 MAC \u5730\u5740\u662f 00-21-27-21-51-EE<\/code>\u3002<\/p>\n\n\n\n
2\uff09\u8be5\u4e3b\u673a\u4f7f\u7528 ARP \u534f\u8bae<\/code>\u786e\u5b9a\u76ee\u7684 MAC \u5730\u5740\u3002
\u5c01\u88c5 ARP \u8bf7\u6c42\u62a5\u6587\u7684\u4ee5\u592a\u7f51\u5e27\u76ee\u7684 MAC \u5730\u5740\u662f\u5e7f\u64ad\u5730\u5740\uff1a<\/p>\n\n\n\n
FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
3\uff09\u4ece\u53d1\u51fa\u56fe 2 \u4e2d\u7684 Web \u8bf7\u6c42\u5f00\u59cb\uff0c\u5230\u6d4f\u89c8\u5668\u6536\u5230\u5168\u90e8\u5185\u5bb9\u4e3a\u6b62\uff0c\u9700\u8981\uff1a<\/p>\n\n\n\n
6 RTT\n<\/code><\/pre>\n\n\n\n
4\uff09\u8be5 IP \u5206\u7ec4\u7ecf\u8fc7\u8def\u7531\u5668 R \u8f6c\u53d1\u65f6\uff0c\u9700\u8981\u4fee\u6539 IP \u9996\u90e8\u4e2d\u7684\u5b57\u6bb5\u4e3b\u8981\u6709\uff1a<\/p>\n\n\n\n
TTL\u3001\u751f\u5b58\u65f6\u95f4\n\u6e90 IP \u5730\u5740\n\u9996\u90e8\u6821\u9a8c\u548c\n<\/code><\/pre>\n\n\n\n
\u5982\u679c\u53ea\u6309\u666e\u901a\u8def\u7531\u8f6c\u53d1\uff0c\u4e0d\u8003\u8651 NAT\uff0c\u5219\u4fee\u6539 TTL<\/code> \u548c \u9996\u90e8\u6821\u9a8c\u548c<\/code>\uff1b\u4f46\u672c\u9898\u4e3b\u673a IP \u662f\u79c1\u6709\u5730\u5740 10.2.128.100<\/code>\uff0c\u8def\u7531\u5668\u5916\u7f51\u63a5\u53e3\u662f 101.12.123.15<\/code>\uff0c\u6240\u4ee5\u5e94\u8003\u8651 NAT\uff0c\u56e0\u6b64\u8fd8\u8981\u4fee\u6539 \u6e90 IP \u5730\u5740<\/code>\u3002<\/p>\n\n\n\n
\n\n\n\n
\u8fd9\u9053\u9898\u672c\u8d28\u4e0a\u662f\u628a\u4e00\u4e2a\u4ee5\u592a\u7f51\u5e27\u4ece\u5934\u62c6\u5f00\uff0c\u8003\u67e5\u201c\u4ee5\u592a\u7f51\u9996\u90e8\u3001IP \u9996\u90e8\u3001TCP \u9996\u90e8\u3001HTTP \u62a5\u6587\u3001ARP\u3001HTTP RTT\u3001\u8def\u7531\u5668\u8f6c\u53d1\/NAT\u201d\u51e0\u4e2a\u77e5\u8bc6\u70b9\u7684\u7efc\u5408\u3002<\/p>\n\n\n\n
\u56fe 2 \u7ed9\u51fa\u7684\u524d 80B \u4ee5\u592a\u7f51\u5e27\u5185\u5bb9\u5f00\u5934\u662f\uff1a<\/p>\n\n\n\n
00 21 27 21 51 ee  00 15 c5 c1 5e 28  08 00  45 00 ...\n<\/code><\/pre>\n\n\n\n
\u4ee5\u592a\u7f51\u5e27\u9996\u90e8\u7ed3\u6784\u662f\uff1a<\/p>\n\n\n\n
\u76ee\u7684 MAC \u5730\u5740\uff1a6B\n\u6e90 MAC \u5730\u5740\uff1a6B\n\u7c7b\u578b\u5b57\u6bb5\uff1a2B\n\u6570\u636e\u5b57\u6bb5\uff1a46~1500B\nCRC\uff1a4B\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u524d 14B \u53ef\u4ee5\u8fd9\u6837\u62c6\uff1a<\/p>\n\n\n\n
\u76ee\u7684 MAC\uff1a00-21-27-21-51-EE\n\u6e90 MAC\uff1a00-15-C5-C1-5E-28\n\u7c7b\u578b\u5b57\u6bb5\uff1a08 00\n<\/code><\/pre>\n\n\n\n
08 00<\/code> \u8868\u793a\u540e\u9762\u5c01\u88c5\u7684\u662f IPv4 \u5206\u7ec4\u3002\u9898\u5e72\u5df2\u7ecf\u7ed9\u51fa\u8be5\u4e3b\u673a MAC \u5730\u5740\u4e3a 00-15-C5-C1-5E-28<\/code>\uff0c\u8fd9\u6b63\u597d\u5bf9\u5e94\u4ee5\u592a\u7f51\u5e27\u4e2d\u7684\u6e90 MAC \u5730\u5740\uff0c\u56e0\u6b64\u8fd9\u4e2a\u5e27\u786e\u5b9e\u662f\u8be5\u4e3b\u673a\u53d1\u51fa\u7684\u3002<\/p>\n\n\n\n
\u8fd9\u91cc\u6700\u5bb9\u6613\u9519\u7684\u5730\u65b9\u662f\uff1a\u8bbf\u95ee Web \u670d\u52a1\u5668\u65f6\uff0c\u4ee5\u592a\u7f51\u5e27\u7684\u76ee\u7684 MAC \u5730\u5740\u4e0d\u4e00\u5b9a\u662f Web \u670d\u52a1\u5668\u7684 MAC \u5730\u5740\u3002\u56e0\u4e3a Web \u670d\u52a1\u5668\u5728 Internet \u4e0a\uff0c\u4e0d\u5728\u672c\u5c40\u57df\u7f51\u5185\uff0c\u6240\u4ee5\u4e3b\u673a\u53d1\u51fa\u7684\u4ee5\u592a\u7f51\u5e27\u53ea\u9700\u8981\u4ea4\u7ed9\u4e0b\u4e00\u8df3\uff0c\u4e5f\u5c31\u662f\u9ed8\u8ba4\u7f51\u5173\u3002\u4e8e\u662f\u56fe 2 \u4e2d\u7684\u76ee\u7684 MAC 00-21-27-21-51-EE<\/code> \u662f\u9ed8\u8ba4\u7f51\u5173\u7684 MAC \u5730\u5740\uff0c\u4e0d\u662f Web \u670d\u52a1\u5668\u7684 MAC \u5730\u5740\u3002<\/p>\n\n\n\n
\u7ee7\u7eed\u770b IP \u9996\u90e8\u3002\u4ee5\u592a\u7f51\u9996\u90e8\u4e4b\u540e\u4ece 45 00<\/code> \u5f00\u59cb\u662f IP \u9996\u90e8\uff1a<\/p>\n\n\n\n
45 00 01 ef 11 3b 40 00 80 06 ba 9d 0a 02 80 64 40 aa 62 20\n<\/code><\/pre>\n\n\n\n
\u5176\u4e2d\uff1a<\/p>\n\n\n\n
45\uff1aIPv4\uff0c\u9996\u90e8\u957f\u5ea6\u4e3a 5 \u00d7 4B = 20B\n01 ef\uff1aIP \u5206\u7ec4\u603b\u957f\u5ea6\uff0c0x01ef = 495B\n80\uff1aTTL = 128\n06\uff1a\u4e0a\u5c42\u534f\u8bae\u662f TCP\n0a 02 80 64\uff1a\u6e90 IP \u5730\u5740\n40 aa 62 20\uff1a\u76ee\u7684 IP \u5730\u5740\n<\/code><\/pre>\n\n\n\n
\u628a\u76ee\u7684 IP \u5730\u5740\u8f6c\u6362\u6210\u5341\u8fdb\u5236\uff1a<\/p>\n\n\n\n
40 aa 62 20\n= 0x40.0xaa.0x62.0x20\n= 64.170.98.32\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5 Web \u670d\u52a1\u5668\u7684 IP \u5730\u5740\u662f 64.170.98.32<\/code>\u3002<\/p>\n\n\n\n
\u6e90 IP \u5730\u5740\uff1a<\/p>\n\n\n\n
0a 02 80 64\n= 10.2.128.100\n<\/code><\/pre>\n\n\n\n
\u8fd9\u6b63\u597d\u662f\u9898\u5e72\u7ed9\u51fa\u7684\u4e3b\u673a IP \u5730\u5740\u3002<\/p>\n\n\n\n
\u7b2c 2 \u95ee\u8003 ARP\u3002\u4e3b\u673a\u8981\u53d1\u4ee5\u592a\u7f51\u5e27\uff0c\u5fc5\u987b\u77e5\u9053\u201c\u4e0b\u4e00\u8df3 IP \u5bf9\u5e94\u7684 MAC \u5730\u5740\u201d\u3002\u7531\u4e8e Web \u670d\u52a1\u5668\u4e0d\u5728\u672c\u5730\u7f51\u7edc\u4e2d\uff0c\u6240\u4ee5\u4e3b\u673a\u4e0d\u662f\u53bb ARP \u67e5\u8be2 64.170.98.32<\/code> \u7684 MAC \u5730\u5740\uff0c\u800c\u662f\u67e5\u8be2\u9ed8\u8ba4\u7f51\u5173 10.2.128.1<\/code> \u7684 MAC \u5730\u5740\u3002<\/p>\n\n\n\n
ARP \u8bf7\u6c42\u662f\u5c40\u57df\u7f51\u5e7f\u64ad\u53d1\u9001\u7684\uff0c\u56e0\u4e3a\u53d1\u9001\u65b9\u6b64\u65f6\u8fd8\u4e0d\u77e5\u9053\u76ee\u6807 MAC \u5730\u5740\uff0c\u6240\u4ee5\u5c01\u88c5 ARP \u8bf7\u6c42\u7684\u4ee5\u592a\u7f51\u5e27\u76ee\u7684 MAC \u5730\u5740\u662f\uff1a<\/p>\n\n\n\n
FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
\u4f46\u662f ARP \u5f97\u5230\u7684\u7ed3\u679c\uff0c\u5373\u9ed8\u8ba4\u7f51\u5173\u7684 MAC \u5730\u5740\uff0c\u5c31\u662f\u4e4b\u540e\u771f\u6b63\u53d1\u9001 Web \u8bf7\u6c42\u65f6\u4ee5\u592a\u7f51\u5e27\u91cc\u7684\u76ee\u7684 MAC \u5730\u5740\uff1a<\/p>\n\n\n\n
00-21-27-21-51-EE\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e24\u4e2a\u5730\u5740\u4e0d\u8981\u6df7\u6dc6\uff1aARP \u8bf7\u6c42\u5e27\u7684\u76ee\u7684 MAC \u662f\u5e7f\u64ad\u5730\u5740\uff1bWeb \u8bf7\u6c42\u6570\u636e\u5e27\u7684\u76ee\u7684 MAC \u662f\u9ed8\u8ba4\u7f51\u5173 MAC\u3002<\/p>\n\n\n\n
\u7b2c 3 \u95ee\u8003 HTTP \u6301\u7eed\u8fde\u63a5\u548c\u975e\u6d41\u6c34\u7ebf\u65b9\u5f0f\u3002<\/p>\n\n\n\n
\u9898\u5e72\u8bf4\uff1a<\/p>\n\n\n\n
HTTP\/1.1 \u534f\u8bae\u4ee5\u6301\u7eed\u7684\u975e\u6d41\u6c34\u7ebf\u65b9\u5f0f\u5de5\u4f5c\n\u4e00\u6b21\u8bf7\u6c42-\u54cd\u5e94\u65f6\u95f4\u4e3a RTT\nrfc.html \u9875\u9762\u5f15\u7528\u4e86 5 \u5e45 JPEG \u5c0f\u56fe\u50cf\n\u4ece\u53d1\u51fa\u56fe 2 \u4e2d\u7684 Web \u8bf7\u6c42\u5f00\u59cb\u8ba1\u7b97\n<\/code><\/pre>\n\n\n\n
\u56fe 2 \u4e2d\u7684\u8bf7\u6c42\u5185\u5bb9\u80fd\u770b\u5230\uff1a<\/p>\n\n\n\n
GET \/rfc.html HTTP\/1.1\n<\/code><\/pre>\n\n\n\n
\u4e5f\u5c31\u662f\u8bf4\u6b64\u65f6\u5df2\u7ecf\u53d1\u51fa\u4e86\u5bf9\u57fa\u672c HTML \u9875\u9762 rfc.html<\/code> \u7684\u8bf7\u6c42\u3002\u6536\u5230\u8fd9\u4e2a HTML \u9875\u9762\u9700\u8981 1 \u4e2a RTT\u3002<\/p>\n\n\n\n
\u6d4f\u89c8\u5668\u6536\u5230\u5e76\u89e3\u6790 rfc.html<\/code> \u540e\uff0c\u53d1\u73b0\u91cc\u9762\u5f15\u7528\u4e86 5 \u5e45 JPEG \u5c0f\u56fe\u50cf\u3002\u7531\u4e8e\u662f\u6301\u7eed\u8fde\u63a5\uff0c\u6240\u4ee5\u4e0d\u9700\u8981\u4e3a\u6bcf\u4e2a\u5bf9\u8c61\u91cd\u65b0\u5efa\u7acb TCP \u8fde\u63a5\uff1b\u4f46\u7531\u4e8e\u662f\u975e\u6d41\u6c34\u7ebf\u65b9\u5f0f\uff0c\u6240\u4ee5\u5fc5\u987b\u7b49\u4e00\u4e2a\u8bf7\u6c42\u7684\u54cd\u5e94\u56de\u6765\u540e\uff0c\u624d\u80fd\u53d1\u9001\u4e0b\u4e00\u4e2a\u8bf7\u6c42\u3002\u4e8e\u662f 5 \u5e45\u5c0f\u56fe\u50cf\u9700\u8981\u4f9d\u6b21\u8bf7\u6c42\uff0c\u5206\u522b\u6d88\u8017 5 \u4e2a RTT\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u603b\u65f6\u95f4\u662f\uff1a<\/p>\n\n\n\n
HTML \u9875\u9762\uff1a1 RTT\n5 \u5e45 JPEG \u5c0f\u56fe\u50cf\uff1a5 RTT\n\u5408\u8ba1\uff1a6 RTT\n<\/code><\/pre>\n\n\n\n
\u56e0\u6b64\u7b54\u6848\u662f 6 RTT<\/code>\u3002<\/p>\n\n\n\n
\u8fd9\u91cc\u5982\u679c\u9898\u76ee\u8bf4\u7684\u662f\u201c\u975e\u6301\u7eed\u8fde\u63a5\u201d\uff0c\u5e76\u4e14\u6bcf\u4e2a\u5bf9\u8c61\u90fd\u8981\u91cd\u65b0\u5efa\u7acb TCP \u8fde\u63a5\uff0c\u5c31\u4f1a\u591a\u7b97 TCP \u5efa\u7acb\u8fde\u63a5\u7684 RTT\uff1b\u5982\u679c\u9898\u76ee\u8bf4\u7684\u662f\u201c\u6301\u7eed\u8fde\u63a5 + \u6d41\u6c34\u7ebf\u201d\uff0c5 \u4e2a\u5c0f\u56fe\u50cf\u7684\u8bf7\u6c42\u53ef\u4ee5\u8fde\u7eed\u53d1\u51fa\uff0cRTT \u6570\u53c8\u4f1a\u51cf\u5c11\u3002\u672c\u9898\u660e\u786e\u662f\u201c\u6301\u7eed\u7684\u975e\u6d41\u6c34\u7ebf\u201d\uff0c\u6240\u4ee5\u662f\u4e00\u4e2a\u5bf9\u8c61\u4e00\u4e2a RTT\uff0c\u4f46\u4e0d\u7528\u91cd\u65b0\u63e1\u624b\u3002<\/p>\n\n\n\n
\u7b2c 4 \u95ee\u8003\u8def\u7531\u5668\u8f6c\u53d1 IP \u5206\u7ec4\u65f6\u5bf9\u9996\u90e8\u5b57\u6bb5\u7684\u4fee\u6539\u3002<\/p>\n\n\n\n
\u5148\u770b\u8be5 IP \u5206\u7ec4\u957f\u5ea6\uff1a<\/p>\n\n\n\n
IP \u603b\u957f\u5ea6 = 0x01ef = 495B\n<\/code><\/pre>\n\n\n\n
\u9898\u56fe\u4e2d\u5916\u7f51\u94fe\u8def MTU \u662f 1500B\uff0c495B \u5c0f\u4e8e 1500B\uff0c\u6240\u4ee5\u4e0d\u9700\u8981\u5206\u7247\u3002\u56e0\u6b64\u4e0d\u9700\u8981\u4fee\u6539\u7247\u504f\u79fb\u3001\u6807\u5fd7\u3001\u603b\u957f\u5ea6\u7b49\u5206\u7247\u76f8\u5173\u5b57\u6bb5\u3002<\/p>\n\n\n\n
\u666e\u901a\u8def\u7531\u5668\u6bcf\u8f6c\u53d1\u4e00\u6b21 IP \u5206\u7ec4\uff0c\u90fd\u4f1a\u628a TTL \u51cf 1\u3002\u539f TTL \u662f\uff1a<\/p>\n\n\n\n
80H = 128\n<\/code><\/pre>\n\n\n\n
\u7ecf\u8fc7 R \u8f6c\u53d1\u540e\u53d8\u6210\uff1a<\/p>\n\n\n\n
127\n<\/code><\/pre>\n\n\n\n
TTL \u53d8\u4e86\uff0cIP \u9996\u90e8\u6821\u9a8c\u548c\u4e5f\u5fc5\u987b\u91cd\u65b0\u8ba1\u7b97\uff0c\u6240\u4ee5\u9996\u90e8\u6821\u9a8c\u548c\u4e5f\u8981\u4fee\u6539\u3002<\/p>\n\n\n\n
\u6b64\u5916\uff0c\u672c\u9898\u7279\u522b\u7ed9\u51fa\u4e3b\u673a IP \u662f\uff1a<\/p>\n\n\n\n
10.2.128.100\n<\/code><\/pre>\n\n\n\n
\u8fd9\u662f\u79c1\u6709\u5730\u5740\u3002\u8def\u7531\u5668\u8fde\u63a5 Internet \u7684\u63a5\u53e3\u5730\u5740\u662f\uff1a<\/p>\n\n\n\n
101.12.123.15\n<\/code><\/pre>\n\n\n\n
\u79c1\u6709\u5730\u5740\u4e0d\u80fd\u76f4\u63a5\u5728 Internet \u4e0a\u8def\u7531\uff0c\u6240\u4ee5 R \u8f6c\u53d1\u5230 Internet \u65f6\u901a\u5e38\u8981\u8fdb\u884c NAT\uff0c\u628a\u6e90 IP \u5730\u5740\u4ece\u79c1\u6709\u5730\u5740\u6539\u4e3a\u8def\u7531\u5668\u5916\u7f51\u63a5\u53e3\u5730\u5740\uff1a<\/p>\n\n\n\n
10.2.128.100  \u2192  101.12.123.15\n<\/code><\/pre>\n\n\n\n
\u56e0\u6b64 IP \u9996\u90e8\u4e2d\u8fd8\u8981\u4fee\u6539\u6e90 IP \u5730\u5740\u3002\u6e90 IP \u4e00\u53d8\uff0cIP \u9996\u90e8\u6821\u9a8c\u548c\u4e5f\u5fc5\u987b\u91cd\u65b0\u8ba1\u7b97\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u7b2c 4 \u95ee\u6309\u672c\u9898\u8bed\u5883\u5e94\u7b54\uff1a<\/p>\n\n\n\n
TTL \u5b57\u6bb5\uff1a\u51cf 1\n\u6e90 IP \u5730\u5740\u5b57\u6bb5\uff1a\u7531 10.2.128.100 \u6539\u4e3a 101.12.123.15\n\u9996\u90e8\u6821\u9a8c\u548c\u5b57\u6bb5\uff1a\u91cd\u65b0\u8ba1\u7b97\n<\/code><\/pre>\n\n\n\n
\u8865\u5145\u4e00\u70b9\uff1a\u5982\u679c\u8fdb\u884c\u7684\u662f NAPT\uff0c\u8def\u7531\u5668\u8fd8\u53ef\u80fd\u4fee\u6539 TCP \u9996\u90e8\u4e2d\u7684\u6e90\u7aef\u53e3\uff0c\u5e76\u91cd\u7b97 TCP \u6821\u9a8c\u548c\u3002\u4f46\u9898\u76ee\u95ee\u7684\u662f\u201cIP \u5206\u7ec4\u5934\u4e2d\u7684\u54ea\u4e9b\u5b57\u6bb5\u201d\uff0c\u6240\u4ee5\u4e3b\u7b54\u6848\u53ea\u5199 IP \u9996\u90e8\u5b57\u6bb5\u5373\u53ef\uff0c\u4e0d\u8981\u628a TCP \u6e90\u7aef\u53e3\u5199\u8fdb IP \u9996\u90e8\u5b57\u6bb5\u91cc\u3002<\/p>\n\n\n\n
\n\n\n\n
\u5b98\u65b9\u7b54\u6848\uff1a1)\u4ee5\u592a\u7f51\u5e27\u7684\u6570\u636e\u90e8\u5206\u662f\u6570\u636e\u62a5\uff0c\u53ea\u8981\u6570\u51fa\u76f8\u5e94\u5b57\u6bb5\u6240\u5728\u7684\u5b57\u8282\u5373\u53ef\u3002\u7531\u56fe3\u53ef\u77e5\u4ee5\u592a\u7f51\u5e27\u9996\u90e8\u67096+6+2=14B,\u7531\u56fe4\u53ef\u77e5\u6570\u636e\u62a5\u9996\u90e8\u7684\u76ee\u7684IP\u5730\u5740\u5b57\u6bb5\u524d\u67094×4=16B\u4ece\u56fe2\u7684\u5e27\u7b2c1\u5b57\u8282\u5f00\u59cb\u657014+16=30B,\u5f97\u5230\u76ee\u7684\u5730\u5740\u4e3a40.aa.62.20(\u5341\u516d\u8fdb\u5236\u6570)\u8f6c\u6362\u6210\u5341\u8fdb\u5236\u6570\u4e3a64.170.98.32\u3002\u7531\u56fe2\u53ef\u77e5\u4ee5\u592a\u7f51\u5e27\u7684\u524d6\u5b57\u8282 00-21-27-21-51-ee\u662f\u76ee\u7684 MAC \u5730\u5740\uff0c\u5373\u4e3a\u4e3b\u673a\u7684\u9ed8\u8ba4\u7f51\u517310.2.128.1\u7aef\u53e3\u7684 MAC \u5730\u5740\u30022)ARP\u7528\u4e8e\u89e3\u51b3PP\u5730\u5740\u5230MAC\u5730\u5740\u7684\u6620\u5c04\u95ee\u9898\u3002\u4e3b\u673a\u7684ARP\u8fdb\u7a0b\u5728\u672c\u4ee5\u592a\u7f51\u4ee5\u5e7f\u64ad\u5f62\u5f0f\u53d1\u9001ARP\u8bf7\u6c42\u5206\u7ec4\uff0c\u5728\u4ee5\u592a\u7f51\u4e0a\u5e7f\u64ad\u65f6\uff0c\u4ee5\u592a\u7f51\u5e27\u7684\u76ee\u7684\u5730\u5740\u4e3a\u51681\uff0c\u5373FF-FF-FF-FF-FF-FF3)HTTP\/1.1\u534f\u8bae\u4ee5\u6301\u7eed\u7684\u975e\u6d41\u6c34\u7ebf\u65b9\u5f0f\u5de5\u4f5c\u65f6\uff0c\u670d\u52a1\u5668\u53d1\u9001\u54cd\u5e94\u540e\u4ecd\u5728\u4e00\u6bb5\u65f6\u95f4\u5185\u4fdd\u6301\u8fd9\u6bb5\u8fde\u63a5\uff0c\u5ba2\u6237\u5728\u6536\u5230\u524d\u4e00\u4e2a\u8bf7\u6c42\u7684\u54cd\u5e94\u540e\u624d\u80fd\u53d1\u51fa\u4e0b\u4e00\u4e2a\u8bf7\u6c42\u3002\u6ce8\u610f\u9898\u76ee\u8bf4\u7684\u662f\u4ece\u53d1\u51faWeb\u8bf7\u6c42\u5f00\u59cb\uff0c\u6240\u4ee5\u6b64\u65f6TCP\u8fde\u63a5\u5df2\u7ecf\u5efa\u7acb\u3002\u7b2c1\u4e2aRTT\u7528\u4e8e\u8bf7\u6c42 Web\u9875\u9762\uff0c\u5ba2\u6237\u6536\u5230\u7b2c\u4e00\u4e2a\u8bf7\u6c42\u7684\u54cd\u5e94\u540e(\u8fd8\u67095\u4e2a\u8bf7\u6c42\u672a\u53d1\u9001)\uff0c\u6bcf\u8bbf\u95ee\u4e00\u6b21\u5bf9\u8c61\u5c31\u7528\u53bb1RTT\u3002\u56e0\u6b64\u5171\u97001+5=6RTT\u540e\u6d4f\u89c8\u5668\u6536\u5230\u5168\u90e8\u5185\u5bb9\u3002
4)\u79c1\u6709\u5730\u5740\u548cInternet\u4e0a\u7684\u4e3b\u673a\u901a\u4fe1\u65f6\uff0c\u987b\u7531NAT\u8def\u7531\u5668\u8fdb\u884c\u7f51\u7edc\u5730\u5740\u8f6c\u6362\uff0c\u628a\u6570\u636e\u62a5\u7684\u6e90IP\u5730\u5740(\u672c\u9898\u4e3a\u79c1\u6709\u5730\u574010.2.128.100)\u8f6c\u6362\u4e3aNAT\u8def\u7531\u5668\u7684\u4e00\u4e2a\u5168\u7403\u5730\u5740(\u672c\u9898\u4e3a 101.12.123.15)\u3002\u56e0\u6b64\uff0c\u6e90\u5730\u5740\u5b57\u6bb50a028064\u53d8\u4e3a65 0c7b 0f\u3002IP \u6570\u636e\u62a5\u6bcf\u7ecf\u8fc7\u4e00\u4e2a\u8def\u7531\u5668\uff0cTTL\u503c\u5c31\u51cf1\uff0c\u5e76\u91cd\u65b0\u8ba1\u7b97\u9996\u90e8\u68c0\u9a8c\u548c\u3002\u82e5\u5206\u7ec4\u7684\u957f\u5ea6\u8d85\u8fc7\u8f93\u51fa\u94fe\u8def\u7684 MTU\uff0c\u5219\u603b\u957f\u5ea6\u5b57\u6bb5\u3001\u6807\u5fd7\u5b57\u6bb5\u3001\u7247\u504f\u79fb\u5b57\u6bb5\u4e5f\u4f1a\u53d1\u751f\u53d8\u5316\u3002 \u89e3\u7b54\u91cc\u9762\u6211\u4eec\u6ce8\u610f\u5230\u4ed6\u505a\u7b2c\u4e00\u5c0f\u95ee\uff0c\u6c42\u6570\u636e\u5305\u4e5f\u8981\u6c42\u90a3\u4e9b\u5185\u5bb9\uff0c\u9ad8\u8d77\u6765\u8ba9\u4eba\u6df7\u6dc6\u3002\u6211\u60f3\u77e5\u9053\uff0c\u5bf9\u4e8e\u8fd9\u79cd\u7c7b\u578b\u7684\u9898\u76ee\uff0c\u770b\u8fd9\u79cd\u6570\u636e\u5305\u91cc\u9762\uff0c\u7136\u540e\u53bb\u533a\u5206\u54ea\u4e00\u5757\u662f\u54ea\u4e00\u5757\u53bb\u627e\u7ec6\u8282\u7684\u90a3\u79cd\u7c7b\u578b\u9898\u76ee\u8be5\u600e\u4e48\u505a\uff1f\u975e\u6d41\u6c34\u7ebf\u65b9\u5f0f\u4e0e\u6d41\u6c34\u7ebf\u6709\u4ec0\u4e48\u533a\u522b\uff1f\u5c31\u662f\u8bf4\u5b83http\u6709\u4e24\u4e2a\u7248\u672c\u7684\u534f\u8bae\uff0c\u80fd\u5426\u91c7\u7528\u6d41\u6c34\uff0c\u80fd\u5426\u8fd0\u884c\u8fd9\u4e9b\u533a\u522b\uff0c\u8be5\u5982\u4f55\u8fdb\u884c\u601d\u8003\u548c\u533a\u5206\u5462\uff1f<\/p>\n\n\n\n
\u5b98\u65b9\u7b54\u6848\u7b2c\u4e00\u95ee\u770b\u8d77\u6765\u7ed5\uff0c\u662f\u56e0\u4e3a\u5b83\u6ca1\u6709\u4ece\u201c\u534f\u8bae\u542b\u4e49\u201d\u5f00\u59cb\u8bb2\uff0c\u800c\u662f\u76f4\u63a5\u7528\u4e86\u201c\u6309\u5b57\u8282\u504f\u79fb\u91cf\u5b9a\u4f4d\u5b57\u6bb5\u201d\u7684\u65b9\u6cd5\u3002\u5bf9\u4e8e\u8fd9\u79cd\u9898\uff0c\u6700\u7a33\u7684\u601d\u8def\u4e0d\u662f\u6b7b\u76ef\u5341\u516d\u8fdb\u5236\u4e32\uff0c\u800c\u662f\u5148\u660e\u786e\u4e00\u4ef6\u4e8b\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u5e27\u91cc\u9762\u88c5\u7684\u662f IP \u6570\u636e\u62a5\uff0cIP \u6570\u636e\u62a5\u91cc\u9762\u88c5\u7684\u662f TCP \u62a5\u6587\u6bb5\uff0cTCP \u62a5\u6587\u6bb5\u91cc\u9762\u624d\u662f HTTP \u8bf7\u6c42\u62a5\u6587\u3002<\/p>\n\n\n\n
\u4e5f\u5c31\u662f\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u5e27\n\u2514\u2500\u2500 IP \u6570\u636e\u62a5\n    \u2514\u2500\u2500 TCP \u62a5\u6587\u6bb5\n        \u2514\u2500\u2500 HTTP \u8bf7\u6c42\u62a5\u6587\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u89e3\u6790\u5341\u516d\u8fdb\u5236\u6570\u636e\u65f6\uff0c\u672c\u8d28\u5c31\u662f\u201c\u5c42\u5c42\u5265\u58f3\u201d\u3002<\/p>\n\n\n\n
\n\n\n\n
\u4e00\u3001\u8fd9\u7c7b\u5341\u516d\u8fdb\u5236\u6570\u636e\u5e27\u9898\u600e\u4e48\u505a<\/h2>\n\n\n\n
\u9047\u5230\u8fd9\u79cd\u9898\uff0c\u5148\u4e0d\u8981\u6025\u7740\u627e\u7b54\u6848\uff0c\u800c\u662f\u5148\u753b\u51fa\u5206\u5c42\u8fb9\u754c\u3002\u56fe 2 \u7684\u5f00\u5934\u662f\uff1a<\/p>\n\n\n\n
00 21 27 21 51 ee  00 15 c5 c1 5e 28  08 00  45 00 ...\n<\/code><\/pre>\n\n\n\n
\u4ee5\u592a\u7f51\u5e27\u9996\u90e8\u56fa\u5b9a\u662f 14B\uff1a<\/p>\n\n\n\n
\u76ee\u7684 MAC \u5730\u5740\uff1a6B\n\u6e90 MAC \u5730\u5740\uff1a6B\n\u7c7b\u578b\u5b57\u6bb5\uff1a2B\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u53ef\u4ee5\u76f4\u63a5\u5207\u5f00\uff1a<\/p>\n\n\n\n
00 21 27 21 51 ee    \u76ee\u7684 MAC\n00 15 c5 c1 5e 28    \u6e90 MAC\n08 00                \u7c7b\u578b\u5b57\u6bb5\uff0c\u8868\u793a\u540e\u9762\u662f IPv4\n45 00 ...             IP \u6570\u636e\u62a5\u5f00\u59cb\n<\/code><\/pre>\n\n\n\n
\u6ce8\u610f\uff0c\u8fd9\u91cc 08 00<\/code> \u662f\u4ee5\u592a\u7f51\u7c7b\u578b\u5b57\u6bb5\uff0c\u8868\u793a\u4ee5\u592a\u7f51\u5e27\u7684\u6570\u636e\u90e8\u5206\u5c01\u88c5\u7684\u662f IPv4 \u6570\u636e\u62a5\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u4ece 45 00<\/code> \u5f00\u59cb\u624d\u662f IP \u9996\u90e8\u3002<\/p>\n\n\n\n
\u5b98\u65b9\u7b54\u6848\u8bf4\u201c\u4ee5\u592a\u7f51\u5e27\u7684\u6570\u636e\u90e8\u5206\u662f\u6570\u636e\u62a5\u201d\uff0c\u8fd9\u91cc\u7684\u201c\u6570\u636e\u62a5\u201d\u6307\u7684\u5c31\u662f IP \u6570\u636e\u62a5\u3002\u4e0d\u8981\u628a\u201c\u4ee5\u592a\u7f51\u5e27\u7684\u6570\u636e\u90e8\u5206\u201d\u548c\u201cHTTP \u6570\u636e\u5185\u5bb9\u201d\u6df7\u5728\u4e00\u8d77\u3002\u4ee5\u592a\u7f51\u5e27\u7684\u6570\u636e\u90e8\u5206\u5e76\u4e0d\u662f\u76f4\u63a5 HTTP\uff0c\u800c\u662f\u5148\u88c5 IP\uff0cIP \u91cc\u9762\u518d\u88c5 TCP\uff0cTCP \u91cc\u9762\u624d\u88c5 HTTP\u3002<\/p>\n\n\n\n
\n\n\n\n
\u4e8c\u3001\u4e3a\u4ec0\u4e48\u76ee\u7684 IP \u8981\u4ece 14 + 16 \u5f00\u59cb\u627e<\/h2>\n\n\n\n
IP \u9996\u90e8\u7ed3\u6784\u4e2d\uff0c\u6e90 IP \u5730\u5740\u548c\u76ee\u7684 IP \u5730\u5740\u5728\u9996\u90e8\u9760\u540e\u7684\u4f4d\u7f6e\u3002\u6807\u51c6 IPv4 \u9996\u90e8\u4e2d\uff1a<\/p>\n\n\n\n
\u7248\u672c + \u9996\u90e8\u957f\u5ea6\uff1a1B\n\u670d\u52a1\u7c7b\u578b\uff1a1B\n\u603b\u957f\u5ea6\uff1a2B\n\u6807\u8bc6\uff1a2B\n\u6807\u5fd7 + \u7247\u504f\u79fb\uff1a2B\nTTL\uff1a1B\n\u534f\u8bae\uff1a1B\n\u9996\u90e8\u68c0\u9a8c\u548c\uff1a2B\n\u6e90 IP \u5730\u5740\uff1a4B\n\u76ee\u7684 IP \u5730\u5740\uff1a4B\n<\/code><\/pre>\n\n\n\n
\u4ece IP \u9996\u90e8\u5f00\u59cb\u7b97\uff0c\u76ee\u7684 IP \u5730\u5740\u524d\u9762\u4e00\u5171\u6709 16B\uff1a<\/p>\n\n\n\n
\u524d 12B\uff1a\u7248\u672c\u3001\u9996\u90e8\u957f\u5ea6\u3001\u670d\u52a1\u7c7b\u578b\u3001\u603b\u957f\u5ea6\u3001\u6807\u8bc6\u3001\u6807\u5fd7\u3001\u7247\u504f\u79fb\u3001TTL\u3001\u534f\u8bae\u3001\u9996\u90e8\u68c0\u9a8c\u548c\n\u518d 4B\uff1a\u6e90 IP \u5730\u5740\n\u5408\u8ba1\uff1a16B\n<\/code><\/pre>\n\n\n\n
\u800c IP \u9996\u90e8\u4e0d\u662f\u4ece\u6574\u4e2a\u4ee5\u592a\u7f51\u5e27\u7b2c 0 \u5b57\u8282\u5f00\u59cb\u7684\uff0c\u800c\u662f\u5728\u4ee5\u592a\u7f51\u9996\u90e8 14B \u4e4b\u540e\u5f00\u59cb\u7684\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u76ee\u7684 IP \u5730\u5740\u5728\u6574\u4e2a\u4ee5\u592a\u7f51\u5e27\u4e2d\u7684\u4f4d\u7f6e\u662f\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u9996\u90e8 14B + IP \u9996\u90e8\u4e2d\u76ee\u7684 IP \u524d\u9762\u7684 16B = \u8df3\u8fc7 30B\n<\/code><\/pre>\n\n\n\n
\u56e0\u6b64\u4ece\u6574\u4e2a\u5e27\u5f00\u5934\u8df3\u8fc7 30B \u540e\uff0c\u63a5\u4e0b\u6765 4B \u5c31\u662f\u76ee\u7684 IP \u5730\u5740\u3002<\/p>\n\n\n\n
\u56fe 2 \u4e2d\u53ef\u4ee5\u5b9a\u4f4d\u5230\uff1a<\/p>\n\n\n\n
40 aa 62 20\n<\/code><\/pre>\n\n\n\n
\u6bcf\u4e2a\u5b57\u8282\u8f6c\u6362\u6210\u5341\u8fdb\u5236\uff1a<\/p>\n\n\n\n
40H = 64\naaH = 170\n62H = 98\n20H = 32\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u76ee\u7684 IP \u5730\u5740\u662f\uff1a<\/p>\n\n\n\n
64.170.98.32\n<\/code><\/pre>\n\n\n\n
\u8fd9\u91cc\u6709\u4e00\u4e2a\u5bb9\u6613\u6df7\u6dc6\u7684\u70b9\uff1a\u5b98\u65b9\u8bf4\u201c\u4ece\u56fe 2 \u7684\u5e27\u7b2c 1 \u5b57\u8282\u5f00\u59cb\u6570 14 + 16 = 30B\u201d\uff0c\u610f\u601d\u4e0d\u662f\u201c\u7b2c 30 \u4e2a\u5b57\u8282\u5c31\u662f\u76ee\u7684 IP\u201d\uff0c\u800c\u662f\u201c\u8df3\u8fc7\u524d 30B\uff0c\u63a5\u4e0b\u6765\u7684 4B \u662f\u76ee\u7684 IP \u5730\u5740\u201d\u3002\u5341\u516d\u8fdb\u5236\u8f6c\u50a8\u91cc\u7ecf\u5e38\u7528\u504f\u79fb\u91cf\uff0c\u6bd4\u5982 0000<\/code>\u30010010<\/code>\u30010020<\/code>\uff0c\u8fd9\u4e9b\u662f\u5730\u5740\u504f\u79fb\uff0c\u4e0d\u662f\u666e\u901a\u884c\u53f7\u3002<\/p>\n\n\n\n
\n\n\n\n
\u4e09\u3001\u505a\u8fd9\u79cd\u9898\u8981\u638c\u63e1\u7684\u5b57\u6bb5\u5b9a\u4f4d\u6a21\u677f<\/h2>\n\n\n\n
\u8fd9\u7c7b\u9898\u6700\u5e38\u8003\u7684\u5b57\u6bb5\u5176\u5b9e\u4e0d\u591a\u3002\u4ee5\u592a\u7f51 + IPv4 + TCP + HTTP \u7ec4\u5408\u9898\uff0c\u5e38\u7528\u6a21\u677f\u5982\u4e0b\u3002<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u5e27\u9996\u90e8\u56fa\u5b9a 14B\uff1a<\/p>\n\n\n\n
\u5b57\u6bb5<\/th>\u957f\u5ea6<\/th>\u4f5c\u7528<\/th><\/tr><\/thead>
\u76ee\u7684 MAC<\/td>6B<\/td>\u5f53\u524d\u94fe\u8def\u4e0b\u4e00\u8df3\u7684 MAC<\/td><\/tr>
\u6e90 MAC<\/td>6B<\/td>\u5f53\u524d\u53d1\u9001\u65b9\u7684 MAC<\/td><\/tr>
\u7c7b\u578b<\/td>2B<\/td>0800<\/code> \u8868\u793a IPv4\uff0c0806<\/code> \u8868\u793a ARP<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
IPv4 \u9996\u90e8\u6700\u5c0f 20B\uff0c\u4f46\u8981\u770b\u9996\u90e8\u957f\u5ea6\u5b57\u6bb5\u3002\u7b2c\u4e00\u4e2a\u5b57\u8282 45<\/code> \u7684\u542b\u4e49\u662f\uff1a<\/p>\n\n\n\n
4\uff1aIPv4\n5\uff1a\u9996\u90e8\u957f\u5ea6 = 5 \u00d7 4B = 20B\n<\/code><\/pre>\n\n\n\n
IPv4 \u9996\u90e8\u5e38\u8003\u5b57\u6bb5\uff1a<\/p>\n\n\n\n
IP \u9996\u90e8\u5185\u504f\u79fb<\/th>\u5b57\u6bb5<\/th>\u957f\u5ea6<\/th><\/tr><\/thead>
0<\/td>\u7248\u672c + \u9996\u90e8\u957f\u5ea6<\/td>1B<\/td><\/tr>
2<\/td>\u603b\u957f\u5ea6<\/td>2B<\/td><\/tr>
4<\/td>\u6807\u8bc6<\/td>2B<\/td><\/tr>
6<\/td>\u6807\u5fd7 + \u7247\u504f\u79fb<\/td>2B<\/td><\/tr>
8<\/td>TTL<\/td>1B<\/td><\/tr>
9<\/td>\u534f\u8bae<\/td>1B<\/td><\/tr>
10<\/td>\u9996\u90e8\u68c0\u9a8c\u548c<\/td>2B<\/td><\/tr>
12<\/td>\u6e90 IP \u5730\u5740<\/td>4B<\/td><\/tr>
16<\/td>\u76ee\u7684 IP \u5730\u5740<\/td>4B<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\u6240\u4ee5\u672c\u9898\u4e2d\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u9996\u90e8 14B\nIP \u9996\u90e8\u4ece\u7b2c 14B \u540e\u5f00\u59cb\n\u6e90 IP \u5730\u5740 = 14 + 12 \u540e\u7684 4B\n\u76ee\u7684 IP \u5730\u5740 = 14 + 16 \u540e\u7684 4B\n<\/code><\/pre>\n\n\n\n
\u56fe 2 \u4e2d\uff1a<\/p>\n\n\n\n
\u6e90 IP\uff1a0a 02 80 64 = 10.2.128.100\n\u76ee\u7684 IP\uff1a40 aa 62 20 = 64.170.98.32\n<\/code><\/pre>\n\n\n\n
TCP \u9996\u90e8\u5728 IP \u9996\u90e8\u4e4b\u540e\u3002\u672c\u9898 IP \u9996\u90e8\u957f\u5ea6\u662f 20B\uff0c\u6240\u4ee5 TCP \u9996\u90e8\u5f00\u59cb\u4f4d\u7f6e\u662f\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u9996\u90e8 14B + IP \u9996\u90e8 20B = 34B\n<\/code><\/pre>\n\n\n\n
TCP \u9996\u90e8\u91cc\u9762\u524d 2B \u662f\u6e90\u7aef\u53e3\uff0c\u540e 2B \u662f\u76ee\u7684\u7aef\u53e3\u3002\u56fe\u4e2d\u53ef\u4ee5\u770b\u5230\uff1a<\/p>\n\n\n\n
04 ff 00 50\n<\/code><\/pre>\n\n\n\n
\u5176\u4e2d\uff1a<\/p>\n\n\n\n
04 ff\uff1a\u6e90\u7aef\u53e3\n00 50\uff1a\u76ee\u7684\u7aef\u53e3 = 80\n<\/code><\/pre>\n\n\n\n
\u76ee\u7684\u7aef\u53e3 80\uff0c\u8bf4\u660e\u8fd9\u662f\u53d1\u5f80 Web \u670d\u52a1\u5668\u7684 HTTP \u8bf7\u6c42\u3002<\/p>\n\n\n\n
TCP \u9996\u90e8\u957f\u5ea6\u4e5f\u8981\u770b TCP \u9996\u90e8\u4e2d\u7684\u6570\u636e\u504f\u79fb\u5b57\u6bb5\u3002\u56fe\u4e2d\u6709\uff1a<\/p>\n\n\n\n
50 18\n<\/code><\/pre>\n\n\n\n
\u5176\u4e2d 50<\/code> \u7684\u9ad8 4 \u4f4d\u662f 5<\/code>\uff0c\u8868\u793a TCP \u9996\u90e8\u957f\u5ea6\u662f\uff1a<\/p>\n\n\n\n
5 \u00d7 4B = 20B\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5 HTTP \u8bf7\u6c42\u62a5\u6587\u4ece\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u9996\u90e8 14B + IP \u9996\u90e8 20B + TCP \u9996\u90e8 20B = 54B\n<\/code><\/pre>\n\n\n\n
\u5904\u5f00\u59cb\u3002<\/p>\n\n\n\n
\u56fe\u4e2d\u540e\u9762\u786e\u5b9e\u80fd\u770b\u5230 ASCII \u5185\u5bb9\uff1a<\/p>\n\n\n\n
47 45 54 20 ...\n<\/code><\/pre>\n\n\n\n
\u8f6c\u6362\u6210\u5b57\u7b26\u5c31\u662f\uff1a<\/p>\n\n\n\n
GET ...\n<\/code><\/pre>\n\n\n\n
\u56e0\u6b64\u8fd9\u662f\u4e00\u4e2a HTTP GET \u8bf7\u6c42\u3002<\/p>\n\n\n\n
\n\n\n\n
\u56db\u3001\u8fd9\u7c7b\u9898\u7684\u6838\u5fc3\u4e0d\u662f\u201c\u80cc\u56fe\u201d\uff0c\u800c\u662f\u5efa\u7acb\u504f\u79fb\u610f\u8bc6<\/h2>\n\n\n\n
\u9047\u5230\u8fd9\u7c7b\u9898\uff0c\u53ef\u4ee5\u6309\u4e0b\u9762\u987a\u5e8f\u505a\uff1a<\/p>\n\n\n\n
\u7b2c\u4e00\u6b65\uff0c\u5148\u5207\u4ee5\u592a\u7f51\u9996\u90e8\u3002\u524d 6B \u662f\u76ee\u7684 MAC\uff0c\u63a5\u7740 6B \u662f\u6e90 MAC\uff0c\u518d 2B \u662f\u7c7b\u578b\u5b57\u6bb5\u3002<\/p>\n\n\n\n
\u7b2c\u4e8c\u6b65\uff0c\u770b\u7c7b\u578b\u5b57\u6bb5\u3002\u5982\u679c\u662f 0800<\/code>\uff0c\u540e\u9762\u662f IPv4\uff1b\u5982\u679c\u662f 0806<\/code>\uff0c\u540e\u9762\u662f ARP\u3002<\/p>\n\n\n\n
\u7b2c\u4e09\u6b65\uff0c\u4ece IP \u9996\u90e8\u7b2c\u4e00\u4e2a\u5b57\u8282\u5224\u65ad IP \u9996\u90e8\u957f\u5ea6\u3002\u4f8b\u5982 45<\/code> \u8868\u793a IPv4\uff0cIP \u9996\u90e8\u957f\u5ea6 20B\u3002<\/p>\n\n\n\n
\u7b2c\u56db\u6b65\uff0c\u6309 IP \u9996\u90e8\u56fa\u5b9a\u4f4d\u7f6e\u627e\u6e90 IP\u3001\u76ee\u7684 IP\u3001TTL\u3001\u534f\u8bae\u5b57\u6bb5\u3002\u534f\u8bae\u5b57\u6bb5\u5982\u679c\u662f 06<\/code>\uff0c\u8bf4\u660e\u4e0a\u5c42\u662f TCP\uff1b\u5982\u679c\u662f 11<\/code>\uff0c\u8bf4\u660e\u4e0a\u5c42\u662f UDP\uff1b\u5982\u679c\u662f 01<\/code>\uff0c\u8bf4\u660e\u662f ICMP\u3002<\/p>\n\n\n\n
\u7b2c\u4e94\u6b65\uff0c\u5982\u679c\u662f TCP\uff0c\u518d\u6839\u636e TCP \u9996\u90e8\u627e\u6e90\u7aef\u53e3\u3001\u76ee\u7684\u7aef\u53e3\uff0c\u5e76\u6839\u636e TCP \u9996\u90e8\u957f\u5ea6\u786e\u5b9a\u5e94\u7528\u5c42\u6570\u636e\u4ece\u54ea\u91cc\u5f00\u59cb\u3002<\/p>\n\n\n\n
\u7b2c\u516d\u6b65\uff0c\u5982\u679c\u5e94\u7528\u5c42\u6570\u636e\u80fd\u8f6c\u6210 ASCII\uff0c\u5c31\u53ef\u4ee5\u8bc6\u522b HTTP \u8bf7\u6c42\u884c\uff0c\u6bd4\u5982 GET \/rfc.html HTTP\/1.1<\/code>\u3002<\/p>\n\n\n\n
\u8fd9\u79cd\u9898\u4e0d\u8981\u4e00\u5f00\u59cb\u5c31\u4ece\u4e00\u5927\u4e32\u5341\u516d\u8fdb\u5236\u91cc\u786c\u627e\u3002\u5e94\u8be5\u5148\u95ee\uff1a\u201c\u73b0\u5728\u6211\u5728\u54ea\u4e00\u5c42\uff1f\u8fd9\u4e00\u5c42\u9996\u90e8\u591a\u957f\uff1f\u4e0b\u4e00\u5c42\u4ece\u54ea\u91cc\u5f00\u59cb\uff1f\u201d<\/p>\n\n\n\n
\n\n\n\n
\u4e94\u3001\u76ee\u7684 MAC \u548c\u76ee\u7684 IP \u4e3a\u4ec0\u4e48\u4e0d\u662f\u4e00\u56de\u4e8b<\/h2>\n\n\n\n
\u8fd9\u9053\u9898\u6700\u5bb9\u6613\u6df7\u7684\u5730\u65b9\u662f\uff1a\u76ee\u7684 MAC \u662f\u9ed8\u8ba4\u7f51\u5173\u7684 MAC\uff0c\u4f46\u76ee\u7684 IP \u662f Web \u670d\u52a1\u5668\u7684 IP\u3002<\/p>\n\n\n\n
\u539f\u56e0\u662f IP \u5730\u5740\u8d1f\u8d23\u7aef\u5230\u7aef\u901a\u4fe1\uff0cMAC \u5730\u5740\u53ea\u8d1f\u8d23\u5f53\u524d\u94fe\u8def\u4e0a\u7684\u4e0b\u4e00\u8df3\u901a\u4fe1\u3002<\/p>\n\n\n\n
\u672c\u9898\u4e2d\u4e3b\u673a\u662f\uff1a<\/p>\n\n\n\n
10.2.128.100\n<\/code><\/pre>\n\n\n\n
Web \u670d\u52a1\u5668\u662f\uff1a<\/p>\n\n\n\n
64.170.98.32\n<\/code><\/pre>\n\n\n\n
\u5b83\u4eec\u4e0d\u5728\u540c\u4e00\u4e2a\u5c40\u57df\u7f51\u5185\uff0c\u6240\u4ee5\u4e3b\u673a\u4e0d\u80fd\u76f4\u63a5\u628a\u4ee5\u592a\u7f51\u5e27\u53d1\u7ed9 Web \u670d\u52a1\u5668\u3002\u4e3b\u673a\u53ea\u80fd\u5148\u628a\u5e27\u53d1\u7ed9\u9ed8\u8ba4\u7f51\u5173 10.2.128.1<\/code>\u3002\u56e0\u6b64\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u5e27\u76ee\u7684 MAC\uff1a\u9ed8\u8ba4\u7f51\u5173\u7684 MAC\nIP \u6570\u636e\u62a5\u76ee\u7684 IP\uff1aWeb \u670d\u52a1\u5668\u7684 IP\n<\/code><\/pre>\n\n\n\n
\u56fe 2 \u524d 6B \u662f\uff1a<\/p>\n\n\n\n
00 21 27 21 51 ee\n<\/code><\/pre>\n\n\n\n
\u8fd9\u662f\u4ee5\u592a\u7f51\u5e27\u7684\u76ee\u7684 MAC\uff0c\u4e5f\u5c31\u662f\u9ed8\u8ba4\u7f51\u5173\u63a5\u53e3\u7684 MAC \u5730\u5740\u3002<\/p>\n\n\n\n
\u800c IP \u9996\u90e8\u4e2d\u7684\u76ee\u7684 IP \u662f\uff1a<\/p>\n\n\n\n
40 aa 62 20 = 64.170.98.32\n<\/code><\/pre>\n\n\n\n
\u8fd9\u662f Web \u670d\u52a1\u5668\u7684 IP \u5730\u5740\u3002<\/p>\n\n\n\n
\u8fd9\u7c7b\u9898\u5e38\u8003\u4e00\u53e5\u8bdd\uff1a<\/p>\n\n\n\n
\u8de8\u7f51\u6bb5\u901a\u4fe1\u65f6\uff0c\u76ee\u7684 IP \u662f\u6700\u7ec8\u76ee\u6807\u4e3b\u673a\uff0c\u76ee\u7684 MAC \u662f\u4e0b\u4e00\u8df3\u8def\u7531\u5668\u3002\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u516d\u3001\u975e\u6d41\u6c34\u7ebf\u65b9\u5f0f\u548c\u6d41\u6c34\u7ebf\u65b9\u5f0f\u7684\u533a\u522b<\/h2>\n\n\n\n
HTTP \u7684 RTT \u9898\uff0c\u6838\u5fc3\u4e0d\u662f\u80cc\u7248\u672c\uff0c\u800c\u662f\u533a\u5206\u4e09\u4e2a\u6982\u5ff5\uff1a<\/p>\n\n\n\n
\u975e\u6301\u7eed\u8fde\u63a5\n\u6301\u7eed\u8fde\u63a5\uff0c\u975e\u6d41\u6c34\u7ebf\n\u6301\u7eed\u8fde\u63a5\uff0c\u6d41\u6c34\u7ebf\n<\/code><\/pre>\n\n\n\n
\u201c\u6301\u7eed\u8fde\u63a5\u201d\u548c\u201c\u6d41\u6c34\u7ebf\u201d\u4e0d\u662f\u4e00\u56de\u4e8b\u3002<\/p>\n\n\n\n
\u6301\u7eed\u8fde\u63a5\u7684\u610f\u601d\u662f\uff1aTCP \u8fde\u63a5\u5efa\u7acb\u540e\uff0c\u53ef\u4ee5\u5728\u540c\u4e00\u4e2a TCP \u8fde\u63a5\u4e0a\u4f20\u591a\u4e2a HTTP \u8bf7\u6c42\u548c\u54cd\u5e94\uff0c\u4e0d\u5fc5\u6bcf\u8bf7\u6c42\u4e00\u4e2a\u5bf9\u8c61\u5c31\u91cd\u65b0\u5efa\u7acb\u4e00\u6b21 TCP \u8fde\u63a5\u3002<\/p>\n\n\n\n
\u6d41\u6c34\u7ebf\u7684\u610f\u601d\u662f\uff1a\u5ba2\u6237\u7aef\u53ef\u4ee5\u4e0d\u7b49\u524d\u4e00\u4e2a\u54cd\u5e94\u56de\u6765\uff0c\u5c31\u8fde\u7eed\u53d1\u9001\u591a\u4e2a\u8bf7\u6c42\u3002<\/p>\n\n\n\n
\u6240\u4ee5\uff1a<\/p>\n\n\n\n
\u6301\u7eed\u8fde\u63a5\u89e3\u51b3\u7684\u662f\uff1aTCP \u8fde\u63a5\u662f\u5426\u590d\u7528\n\u6d41\u6c34\u7ebf\u89e3\u51b3\u7684\u662f\uff1a\u591a\u4e2a HTTP \u8bf7\u6c42\u662f\u5426\u53ef\u4ee5\u8fde\u7eed\u53d1\u51fa\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u4e03\u3001HTTP\/1.0\u3001HTTP\/1.1 \u548c\u6d41\u6c34\u7ebf\u600e\u4e48\u533a\u5206<\/h2>\n\n\n\n
\u5728\u8003\u7814\u8bed\u5883\u4e2d\uff0c\u901a\u5e38\u8fd9\u6837\u7406\u89e3\uff1a<\/p>\n\n\n\n
\u7c7b\u578b<\/th>\u9ed8\u8ba4\u8fde\u63a5\u65b9\u5f0f<\/th>\u662f\u5426\u8003\u8651\u6d41\u6c34\u7ebf<\/th><\/tr><\/thead>
HTTP\/1.0<\/td>\u9ed8\u8ba4\u975e\u6301\u7eed\u8fde\u63a5<\/td>\u4e00\u822c\u4e0d\u8003\u8651\u6d41\u6c34\u7ebf<\/td><\/tr>
HTTP\/1.1<\/td>\u9ed8\u8ba4\u6301\u7eed\u8fde\u63a5<\/td>\u53ef\u4ee5\u6709\u975e\u6d41\u6c34\u7ebf\u6216\u6d41\u6c34\u7ebf\uff0c\u9898\u76ee\u4f1a\u8bf4\u660e<\/td><\/tr>
HTTP\/2<\/td>\u591a\u8def\u590d\u7528<\/td>\u4e00\u822c\u4e0d\u662f 408 \u4f20\u7edf RTT \u9898\u91cd\u70b9<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
HTTP\/1.0 \u9ed8\u8ba4\u662f\u975e\u6301\u7eed\u8fde\u63a5\uff0c\u4e5f\u5c31\u662f\u6bcf\u8bf7\u6c42\u4e00\u4e2a\u5bf9\u8c61\uff0c\u901a\u5e38\u90fd\u8981\u5efa\u7acb\u4e00\u4e2a\u65b0\u7684 TCP \u8fde\u63a5\uff0c\u54cd\u5e94\u7ed3\u675f\u540e\u8fde\u63a5\u5173\u95ed\u3002\u5f53\u7136 HTTP\/1.0 \u540e\u6765\u4e5f\u6709 Keep-Alive \u6269\u5c55\uff0c\u4f46\u8003\u7814\u9898\u5982\u679c\u6ca1\u7279\u522b\u8bf4\u660e\uff0c\u4e00\u822c\u6309\u9ed8\u8ba4\u975e\u6301\u7eed\u8fde\u63a5\u5904\u7406\u3002<\/p>\n\n\n\n
HTTP\/1.1 \u9ed8\u8ba4\u662f\u6301\u7eed\u8fde\u63a5\uff0c\u4e5f\u5c31\u662f\u4e00\u4e2a TCP \u8fde\u63a5\u53ef\u4ee5\u590d\u7528\u3002\u4f46 HTTP\/1.1 \u6301\u7eed\u8fde\u63a5\u53c8\u5206\u4e3a\u975e\u6d41\u6c34\u7ebf\u548c\u6d41\u6c34\u7ebf\u4e24\u79cd\u60c5\u51b5\u3002<\/p>\n\n\n\n
\u672c\u9898\u660e\u786e\u8bf4\uff1a<\/p>\n\n\n\n
HTTP\/1.1 \u534f\u8bae\u4ee5\u6301\u7eed\u7684\u975e\u6d41\u6c34\u7ebf\u65b9\u5f0f\u5de5\u4f5c\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u4e0d\u80fd\u53ea\u770b\u5230 HTTP\/1.1 \u5c31\u9ed8\u8ba4\u201c\u5168\u90e8\u8bf7\u6c42\u4e00\u8d77\u53d1\u201d\u3002\u9898\u76ee\u5df2\u7ecf\u9650\u5b9a\u4e3a\u975e\u6d41\u6c34\u7ebf\u3002<\/p>\n\n\n\n
\n\n\n\n
\u516b\u3001\u6301\u7eed\u975e\u6d41\u6c34\u7ebf\u5982\u4f55\u8ba1\u7b97 RTT<\/h2>\n\n\n\n
\u6301\u7eed\u975e\u6d41\u6c34\u7ebf\u7684\u7279\u70b9\u662f\uff1a<\/p>\n\n\n\n
\u540c\u4e00\u4e2a TCP \u8fde\u63a5\u53ef\u4ee5\u590d\u7528\n\u4f46\u5fc5\u987b\u6536\u5230\u524d\u4e00\u4e2a\u54cd\u5e94\u540e\uff0c\u624d\u80fd\u53d1\u9001\u4e0b\u4e00\u4e2a\u8bf7\u6c42\n<\/code><\/pre>\n\n\n\n
\u672c\u9898\u8bf4\u201c\u4ece\u53d1\u51fa\u56fe 2 \u4e2d\u7684 Web \u8bf7\u6c42\u5f00\u59cb\u201d\uff0c\u8bf4\u660e\u6b64\u65f6 TCP \u8fde\u63a5\u5df2\u7ecf\u5efa\u7acb\uff0c\u4e0d\u9700\u8981\u518d\u7b97 TCP \u4e09\u6b21\u63e1\u624b\u7684 1 \u4e2a RTT\u3002<\/p>\n\n\n\n
\u56fe 2 \u4e2d\u8bf7\u6c42\u7684\u662f\uff1a<\/p>\n\n\n\n
GET \/rfc.html HTTP\/1.1\n<\/code><\/pre>\n\n\n\n
\u6536\u5230\u8fd9\u4e2a HTML \u9875\u9762\u9700\u8981 1 RTT\u3002<\/p>\n\n\n\n
\u6d4f\u89c8\u5668\u6536\u5230\u5e76\u89e3\u6790 HTML \u9875\u9762\u540e\uff0c\u53d1\u73b0\u91cc\u9762\u5f15\u7528\u4e86 5 \u5e45 JPEG \u5c0f\u56fe\u50cf\u3002\u7531\u4e8e\u662f\u975e\u6d41\u6c34\u7ebf\uff0c5 \u5e45\u56fe\u7247\u4e0d\u80fd\u4e00\u6b21\u6027\u628a\u8bf7\u6c42\u5168\u90e8\u53d1\u51fa\u53bb\uff0c\u800c\u662f\u5fc5\u987b\u8fd9\u6837\uff1a<\/p>\n\n\n\n
\u8bf7\u6c42\u56fe\u72471 -> \u7b49\u54cd\u5e94\u56de\u6765\n\u8bf7\u6c42\u56fe\u72472 -> \u7b49\u54cd\u5e94\u56de\u6765\n\u8bf7\u6c42\u56fe\u72473 -> \u7b49\u54cd\u5e94\u56de\u6765\n\u8bf7\u6c42\u56fe\u72474 -> \u7b49\u54cd\u5e94\u56de\u6765\n\u8bf7\u6c42\u56fe\u72475 -> \u7b49\u54cd\u5e94\u56de\u6765\n<\/code><\/pre>\n\n\n\n
\u6bcf\u4e2a\u5bf9\u8c61 1 RTT\uff0c\u6240\u4ee5\uff1a<\/p>\n\n\n\n
rfc.html\uff1a1 RTT\n5 \u5e45 JPEG\uff1a5 RTT\n\u5408\u8ba1\uff1a6 RTT\n<\/code><\/pre>\n\n\n\n
\u56e0\u6b64\u672c\u9898\u7b54\u6848\u662f\uff1a<\/p>\n\n\n\n
6 RTT\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u4e5d\u3001\u5982\u679c\u662f\u6d41\u6c34\u7ebf\u65b9\u5f0f\uff0c\u4f1a\u600e\u4e48\u7b97<\/h2>\n\n\n\n
\u5982\u679c\u9898\u76ee\u6539\u6210\u201cHTTP\/1.1 \u6301\u7eed\u8fde\u63a5\uff0c\u6d41\u6c34\u7ebf\u65b9\u5f0f\u201d\uff0c\u90a3\u4e48\u6d41\u7a0b\u4e0d\u540c\u3002<\/p>\n\n\n\n
\u4ecd\u7136\u8981\u5148\u8bf7\u6c42 rfc.html<\/code>\uff0c\u56e0\u4e3a\u6d4f\u89c8\u5668\u5fc5\u987b\u5148\u62ff\u5230 HTML \u9875\u9762\uff0c\u89e3\u6790\u540e\u624d\u77e5\u9053\u91cc\u9762\u5f15\u7528\u4e86\u54ea 5 \u5e45\u56fe\u7247\u3002<\/p>\n\n\n\n
\u6240\u4ee5 HTML \u9875\u9762\u4ecd\u7136\u9700\u8981\uff1a<\/p>\n\n\n\n
1 RTT\n<\/code><\/pre>\n\n\n\n
\u4f46\u662f\u89e3\u6790\u51fa 5 \u5e45 JPEG \u540e\uff0c\u6d41\u6c34\u7ebf\u65b9\u5f0f\u5141\u8bb8\u5ba2\u6237\u7aef\u8fde\u7eed\u53d1\u51fa 5 \u4e2a\u8bf7\u6c42\uff0c\u800c\u4e0d\u7528\u7b49\u524d\u4e00\u4e2a\u54cd\u5e94\u56de\u6765\u3002<\/p>\n\n\n\n
\u7406\u60f3\u60c5\u51b5\u4e0b\uff0c\u8fd9 5 \u4e2a\u56fe\u7247\u8bf7\u6c42\u53ef\u4ee5\u5408\u5e76\u770b\u6210\u518d\u7528\uff1a<\/p>\n\n\n\n
1 RTT\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u4ece\u5df2\u7ecf\u53d1\u51fa\u7b2c\u4e00\u4e2a Web \u8bf7\u6c42\u5f00\u59cb\u7b97\uff1a<\/p>\n\n\n\n
HTML \u9875\u9762\uff1a1 RTT\n5 \u5e45\u56fe\u7247\u6d41\u6c34\u7ebf\u8bf7\u6c42\uff1a1 RTT\n\u5408\u8ba1\uff1a2 RTT\n<\/code><\/pre>\n\n\n\n
\u5982\u679c\u9898\u76ee\u4ece\u201c\u5f00\u59cb\u5efa\u7acb TCP \u8fde\u63a5\u201d\u7b97\uff0c\u8fd8\u8981\u989d\u5916\u52a0\u4e0a TCP \u4e09\u6b21\u63e1\u624b\u7684 1 RTT\u3002<\/p>\n\n\n\n
\n\n\n\n
\u5341\u3001HTTP RTT \u9898\u7684\u5e38\u7528\u5224\u65ad\u516c\u5f0f<\/h2>\n\n\n\n
\u5047\u8bbe\u4e00\u4e2a HTML \u9875\u9762\u5f15\u7528\u4e86 N \u4e2a\u5c0f\u5bf9\u8c61\uff0c\u5e76\u4e14\u4e0d\u8003\u8651 DNS\u3001\u4f20\u8f93\u65f6\u5ef6\u3001\u670d\u52a1\u5668\u5904\u7406\u65f6\u5ef6\uff0c\u53ea\u6309 RTT \u8ba1\u7b97\u3002<\/p>\n\n\n\n
\u5982\u679c\u9898\u76ee\u8bf4\u201c\u4ece\u53d1\u51fa Web \u8bf7\u6c42\u5f00\u59cb\u201d\uff0c\u8bf4\u660e TCP \u5df2\u7ecf\u5efa\u7acb\uff0c\u5e38\u89c1\u7ed3\u8bba\u662f\uff1a<\/p>\n\n\n\n
\u65b9\u5f0f<\/th>RTT \u6570<\/th><\/tr><\/thead>
\u6301\u7eed\u8fde\u63a5\uff0c\u975e\u6d41\u6c34\u7ebf<\/td>1 + N<\/td><\/tr>
\u6301\u7eed\u8fde\u63a5\uff0c\u6d41\u6c34\u7ebf<\/td>1 + 1<\/td><\/tr>
\u975e\u6301\u7eed\u8fde\u63a5\uff0c\u4e32\u884c\u8bf7\u6c42<\/td>1 + 2N<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\u8fd9\u91cc\u7684 1<\/code> \u662f\u8bf7\u6c42\u57fa\u672c HTML \u9875\u9762\u3002\u975e\u6301\u7eed\u8fde\u63a5\u4e0b\uff0c\u540e\u9762\u6bcf\u4e2a\u5d4c\u5165\u5bf9\u8c61\u90fd\u8981\u91cd\u65b0\u5efa\u7acb TCP \u8fde\u63a5\uff0c\u6240\u4ee5\u6bcf\u4e2a\u5bf9\u8c61\u7ea6 2 RTT\uff1a\u4e00\u4e2a RTT \u5efa\u7acb\u8fde\u63a5\uff0c\u4e00\u4e2a RTT \u8bf7\u6c42\u54cd\u5e94\u3002<\/p>\n\n\n\n
\u5982\u679c\u9898\u76ee\u8bf4\u201c\u4ece\u7528\u6237\u70b9\u51fb\u94fe\u63a5\u5f00\u59cb\u201d\u6216\u8005\u201c\u4ece\u5efa\u7acb TCP \u8fde\u63a5\u5f00\u59cb\u201d\uff0c\u5c31\u8981\u6ce8\u610f\u662f\u5426\u8981\u52a0 TCP \u4e09\u6b21\u63e1\u624b\u7684 1 RTT\u3002\u5982\u679c\u8fd8\u6d89\u53ca DNS \u67e5\u8be2\uff0c\u8fd8\u8981\u628a DNS \u67e5\u8be2\u65f6\u95f4\u4e5f\u7b97\u8fdb\u53bb\u3002<\/p>\n\n\n\n
\u672c\u9898\u9898\u5e72\u4e13\u95e8\u8bf4\u201c\u4ece\u53d1\u51fa\u56fe 2 \u4e2d\u7684 Web \u8bf7\u6c42\u5f00\u59cb\u201d\uff0c\u5c31\u662f\u4e3a\u4e86\u544a\u8bc9\u8003\u751f\uff1a\u4e0d\u8981\u518d\u52a0 TCP \u5efa\u7acb\u8fde\u63a5\u7684 RTT\u3002<\/p>\n\n\n\n
\n\n\n\n
\u5341\u4e00\u3001\u8fd9\u9053\u9898\u7684\u6613\u9519\u70b9\u603b\u7ed3<\/h2>\n\n\n\n
\u7b2c\u4e00\uff0c\u770b\u5230\u76ee\u7684 MAC\uff0c\u4e0d\u8981\u4ee5\u4e3a\u5b83\u5c31\u662f Web \u670d\u52a1\u5668\u7684 MAC\u3002\u8de8\u7f51\u6bb5\u901a\u4fe1\u65f6\uff0c\u4ee5\u592a\u7f51\u5e27\u7684\u76ee\u7684 MAC \u662f\u4e0b\u4e00\u8df3\u8def\u7531\u5668\uff0c\u4e5f\u5c31\u662f\u9ed8\u8ba4\u7f51\u5173\u7684 MAC\u3002<\/p>\n\n\n\n
\u7b2c\u4e8c\uff0c\u770b\u5230\u76ee\u7684 IP\uff0c\u624d\u662f\u6700\u7ec8\u76ee\u6807 Web \u670d\u52a1\u5668\u3002IP \u5730\u5740\u7aef\u5230\u7aef\u4e0d\u53d8\uff0cMAC \u5730\u5740\u9010\u8df3\u53d8\u5316\u3002\u82e5\u6709 NAT\uff0c\u6e90 IP \u4f1a\u5728 NAT \u8def\u7531\u5668\u5904\u88ab\u6539\u5199\u3002<\/p>\n\n\n\n
\u7b2c\u4e09\uff0c\u89e3\u6790\u5341\u516d\u8fdb\u5236\u6570\u636e\u65f6\uff0c\u4e0d\u8981\u628a\u4ee5\u592a\u7f51\u5e27\u3001IP \u6570\u636e\u62a5\u3001TCP \u62a5\u6587\u6bb5\u3001HTTP \u8bf7\u6c42\u6df7\u6210\u4e00\u5c42\u3002\u8981\u5148\u5207 14B \u4ee5\u592a\u7f51\u9996\u90e8\uff0c\u518d\u770b IP \u9996\u90e8\uff0c\u518d\u770b TCP \u9996\u90e8\u3002<\/p>\n\n\n\n
\u7b2c\u56db\uff0cHTTP\/1.1 \u9ed8\u8ba4\u6301\u7eed\u8fde\u63a5\uff0c\u4f46\u6301\u7eed\u8fde\u63a5\u4e0d\u7b49\u4e8e\u6d41\u6c34\u7ebf\u3002\u9898\u76ee\u5982\u679c\u8bf4\u201c\u6301\u7eed\u975e\u6d41\u6c34\u7ebf\u201d\uff0c\u5c31\u5fc5\u987b\u4e00\u4e2a\u8bf7\u6c42\u54cd\u5e94\u7ed3\u675f\u540e\u518d\u53d1\u4e0b\u4e00\u4e2a\u8bf7\u6c42\u3002<\/p>\n\n\n\n
\u7b2c\u4e94\uff0cRTT \u9898\u8981\u7279\u522b\u770b\u8d77\u7b97\u70b9\u3002\u9898\u76ee\u8bf4\u201c\u4ece\u53d1\u51fa Web \u8bf7\u6c42\u5f00\u59cb\u201d\uff0c\u901a\u5e38\u8868\u793a TCP \u8fde\u63a5\u5df2\u7ecf\u5efa\u7acb\uff0c\u4e0d\u518d\u8ba1\u7b97\u4e09\u6b21\u63e1\u624b\u7684 1 RTT\u3002<\/p>\n\n\n\n
\u6700\u540e\u53ef\u4ee5\u628a\u8fd9\u7c7b\u9898\u538b\u7f29\u6210\u4e00\u53e5\u505a\u9898\u53e3\u8bc0\uff1a<\/p>\n\n\n\n
\u5148\u5265\u4ee5\u592a\u7f51\uff0c\u518d\u5265 IP\uff0c\u518d\u5265 TCP\uff0c\u6700\u540e\u770b HTTP\uff1b\nMAC \u770b\u4e0b\u4e00\u8df3\uff0cIP \u770b\u6700\u7ec8\u7aef\uff1b\n\u6301\u7eed\u770b\u662f\u5426\u590d\u7528\u8fde\u63a5\uff0c\u6d41\u6c34\u770b\u662f\u5426\u8fde\u7eed\u53d1\u8bf7\u6c42\uff1b\nRTT \u5148\u770b\u8d77\u7b97\u70b9\uff0c\u518d\u770b\u5bf9\u8c61\u6570\u3002\n<\/code><\/pre>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u672c\u9898\u7ed3\u8bba\uff1a<\/p>\n\n\n\n
1\uff09H1 \u9664\u4e86 HTTP\uff0c\u8fd8\u8fd0\u884c\u4e86 DNS<\/code> \u5e94\u7528\u5c42\u534f\u8bae\uff0c\u7528\u4e8e\u628a\u57df\u540d www.abc.com<\/code> \u89e3\u6790\u6210 Web \u670d\u52a1\u5668\u7684 IP \u5730\u5740\u3002DNS \u62a5\u6587\u4ece\u5e94\u7528\u5c42\u5230\u6570\u636e\u94fe\u8def\u5c42\u7684\u5c01\u88c5\u8fc7\u7a0b\u662f\uff1a<\/p>\n\n\n\n
DNS \u62a5\u6587 \u2192 UDP \u6570\u636e\u62a5 \u2192 IP \u6570\u636e\u62a5 \u2192 \u4ee5\u592a\u7f51\u5e27\n<\/code><\/pre>\n\n\n\n
\u53e6\u5916\uff0c\u4e3a\u4e86\u628a IP \u6570\u636e\u62a5\u5c01\u88c5\u6210\u4ee5\u592a\u7f51\u5e27\uff0cH1 \u8fd8\u9700\u8981\u4f7f\u7528 ARP<\/code> \u83b7\u53d6\u76ee\u7684 MAC \u5730\u5740\uff0c\u4f46 ARP \u4e0d\u662f DNS \u62a5\u6587\u7684\u201c\u9010\u5c42\u5c01\u88c5\u534f\u8bae\u201d\uff0c\u800c\u662f\u4e3a\u53d1\u9001\u4ee5\u592a\u7f51\u5e27\u670d\u52a1\u7684\u5730\u5740\u89e3\u6790\u534f\u8bae\u3002<\/p>\n\n\n\n
2\uff09t1 \u65f6\u523b\uff0cS \u7684\u4ea4\u6362\u8868\u5185\u5bb9\u81f3\u5c11\u4e3a\uff1a<\/p>\n\n\n\n
<00-11-22-33-44-cc, 4>\n<00-11-22-33-44-bb, 1>\n<00-11-22-33-44-aa, 2>\n<\/code><\/pre>\n\n\n\n
\u4e5f\u5c31\u662f\uff1a<\/p>\n\n\n\n
H1 \u7684 MAC \u5730\u5740 \u2192 \u7aef\u53e3 4\n\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u7684 MAC \u5730\u5740 \u2192 \u7aef\u53e3 1\n\u8def\u7531\u5668 R \u7684 MAC \u5730\u5740 \u2192 \u7aef\u53e3 2\n<\/code><\/pre>\n\n\n\n
\u4e0d\u4f1a\u6709 H2 \u7684\u8868\u9879\uff0c\u56e0\u4e3a H2 \u5728\u8fd9\u4e2a\u8fc7\u7a0b\u4e2d\u6ca1\u6709\u53d1\u9001\u5e27\uff0c\u4ea4\u6362\u673a\u53ea\u80fd\u6839\u636e\u201c\u6536\u5230\u5e27\u7684\u6e90 MAC \u5730\u5740\u201d\u5b66\u4e60\u8868\u9879\u3002<\/p>\n\n\n\n
3\uff09\u4ece t0 \u5230 t1 \u671f\u95f4\uff0cH2 \u81f3\u5c11\u6536\u5230 2 \u4e2a<\/code>\u4e0e\u6b64\u6b21 Web \u8bbf\u95ee\u76f8\u5173\u7684\u5e27\u3002\u8fd9\u4e24\u4e2a\u5e27\u90fd\u662f ARP \u8bf7\u6c42\u5e7f\u64ad\u5e27\uff0c\u76ee\u7684 MAC \u5730\u5740\u5747\u4e3a\uff1a<\/p>\n\n\n\n
FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u8fd9\u9053\u9898\u7684\u4e3b\u7ebf\u662f\uff1aH1 \u8bbf\u95ee www.abc.com<\/code>\uff0c\u5148\u8981\u505a\u57df\u540d\u89e3\u6790\uff0c\u518d\u53d1\u9001 HTTP \u8bf7\u6c42\u3002\u56e0\u4e3a t0 \u65f6\u523b H1 \u7684 ARP \u8868\u548c S \u7684\u4ea4\u6362\u8868\u90fd\u662f\u7a7a\u7684\uff0c\u6240\u4ee5\u4e2d\u95f4\u4f1a\u53d1\u751f ARP \u5e7f\u64ad\u3001DNS \u67e5\u8be2\u3001ARP \u5e7f\u64ad\u3001HTTP \u8bf7\u6c42\u8fd9\u51e0\u4e2a\u9636\u6bb5\u3002<\/p>\n\n\n\n
\u5148\u770b\u62d3\u6251\u4e2d\u7684\u5730\u5740\uff1a<\/p>\n\n\n\n
H1\uff1a192.168.1.2\/25\uff0cMAC = 00-11-22-33-44-cc\uff0c\u63a5 S \u7684 4 \u53f7\u7aef\u53e3\nH2\uff1a192.168.1.3\/25\uff0cMAC = 00-11-22-33-44-dd\uff0c\u63a5 S \u7684 3 \u53f7\u7aef\u53e3\n\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\uff1a192.168.1.126\/25\uff0cMAC = 00-11-22-33-44-bb\uff0c\u63a5 S \u7684 1 \u53f7\u7aef\u53e3\n\u8def\u7531\u5668 R \u5185\u7f51\u63a5\u53e3\uff1a192.168.1.1\/25\uff0cMAC = 00-11-22-33-44-aa\uff0c\u63a5 S \u7684 2 \u53f7\u7aef\u53e3\n<\/code><\/pre>\n\n\n\n
\u8fd9\u91cc\u7684 \/25<\/code> \u8868\u793a\u5b50\u7f51\u63a9\u7801\u662f\uff1a<\/p>\n\n\n\n
255.255.255.128\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u672c\u5730\u5b50\u7f51\u8303\u56f4\u662f\uff1a<\/p>\n\n\n\n
192.168.1.0 ~ 192.168.1.127\n<\/code><\/pre>\n\n\n\n
H1\u3001H2\u3001\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u3001\u8def\u7531\u5668 R \u7684\u5185\u7f51\u63a5\u53e3\u90fd\u5728\u540c\u4e00\u4e2a\u5c40\u57df\u7f51\u4e2d\u3002\u56e0\u6b64 H1 \u8981\u8bbf\u95ee\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u65f6\uff0c\u53ef\u4ee5\u76f4\u63a5\u53d1\u7ed9\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\uff1bH1 \u8981\u8bbf\u95ee Internet \u4e0a\u7684 Web \u670d\u52a1\u5668\u65f6\uff0c\u5219\u9700\u8981\u628a\u5e27\u4ea4\u7ed9\u9ed8\u8ba4\u7f51\u5173 R\u3002<\/p>\n\n\n\n
\n\n\n\n
H1 \u5728\u6d4f\u89c8\u5668\u4e2d\u8bbf\u95ee www.abc.com<\/code>\uff0c\u4e0d\u80fd\u4e00\u5f00\u59cb\u5c31\u53d1 HTTP \u8bf7\u6c42\uff0c\u56e0\u4e3a HTTP \u8bf7\u6c42\u9700\u8981\u77e5\u9053 Web \u670d\u52a1\u5668\u7684 IP \u5730\u5740\u3002\u7528\u6237\u8f93\u5165\u7684\u662f\u57df\u540d\uff0c\u6240\u4ee5\u9996\u5148\u8981\u505a DNS \u89e3\u6790\u3002<\/p>\n\n\n\n
DNS \u662f\u5e94\u7528\u5c42\u534f\u8bae\u3002\u5e38\u89c4\u60c5\u51b5\u4e0b\uff0cDNS \u67e5\u8be2\u62a5\u6587\u5c01\u88c5\u5728 UDP \u4e2d\uff0cUDP \u518d\u5c01\u88c5\u8fdb IP\uff0cIP \u518d\u5c01\u88c5\u8fdb\u4ee5\u592a\u7f51\u5e27\u3002\u56e0\u6b64\u7b2c 1 \u95ee\u5e94\u7b54\u4e3a\uff1a<\/p>\n\n\n\n
\u5e94\u7528\u5c42\u534f\u8bae\uff1aDNS\n\u5c01\u88c5\u8fc7\u7a0b\uff1aDNS \u2192 UDP \u2192 IP \u2192 Ethernet\n<\/code><\/pre>\n\n\n\n
\u8fd9\u91cc\u6709\u4e2a\u5bb9\u6613\u6df7\u7684\u70b9\uff1aARP \u4e00\u5b9a\u4f1a\u51fa\u73b0\uff0c\u4f46\u5b83\u4e0d\u662f DNS \u62a5\u6587\u4ece\u5e94\u7528\u5c42\u5411\u4e0b\u5c01\u88c5\u7684\u4e00\u5c42\u3002DNS \u62a5\u6587\u4e0d\u4f1a\u5c01\u88c5\u5728 ARP \u91cc\u9762\u3002ARP \u7684\u4f5c\u7528\u662f\uff1a\u5728\u53d1\u9001\u4ee5\u592a\u7f51\u5e27\u4e4b\u524d\uff0c\u5148\u628a\u4e0b\u4e00\u8df3 IP \u5730\u5740\u89e3\u6790\u6210 MAC \u5730\u5740\u3002<\/p>\n\n\n\n
\n\n\n\n
\u4ece t0 \u5230 t1 \u7684\u8fc7\u7a0b\u53ef\u4ee5\u6309\u65f6\u95f4\u987a\u5e8f\u62c6\u5f00\u3002<\/p>\n\n\n\n
\u7b2c\u4e00\u6b65\uff0cH1 \u8981\u5411\u672c\u5730\u57df\u540d\u670d\u52a1\u5668 192.168.1.126<\/code> \u53d1\u9001 DNS \u67e5\u8be2\u3002\u7531\u4e8e H1 \u7684 ARP \u8868\u4e3a\u7a7a\uff0c\u5b83\u4e0d\u77e5\u9053\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u7684 MAC \u5730\u5740\uff0c\u6240\u4ee5 H1 \u5148\u53d1\u9001 ARP \u8bf7\u6c42\uff1a<\/p>\n\n\n\n
\u8c01\u662f 192.168.1.126\uff1f\u8bf7\u544a\u8bc9 192.168.1.2\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a ARP \u8bf7\u6c42\u5c01\u88c5\u6210\u4ee5\u592a\u7f51\u5e27\u65f6\uff0c\u76ee\u7684 MAC \u662f\u5e7f\u64ad\u5730\u5740\uff1a<\/p>\n\n\n\n
FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
\u6e90 MAC \u662f H1 \u7684 MAC\uff1a<\/p>\n\n\n\n
00-11-22-33-44-cc\n<\/code><\/pre>\n\n\n\n
\u8be5\u5e27\u4ece S \u7684 4 \u53f7\u7aef\u53e3\u8fdb\u5165\u4ea4\u6362\u673a\u3002\u4ea4\u6362\u673a\u6536\u5230\u5e27\u540e\uff0c\u6839\u636e\u6e90 MAC \u5b66\u4e60\u5230\uff1a<\/p>\n\n\n\n
<00-11-22-33-44-cc, 4>\n<\/code><\/pre>\n\n\n\n
\u56e0\u4e3a\u8fd9\u662f\u5e7f\u64ad\u5e27\uff0cS \u4f1a\u4ece\u9664 4 \u53f7\u7aef\u53e3\u4ee5\u5916\u7684\u5176\u4ed6\u7aef\u53e3\u8f6c\u53d1\u51fa\u53bb\uff0c\u6240\u4ee5\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u3001R\u3001H2 \u90fd\u4f1a\u6536\u5230\u8fd9\u4e2a ARP \u8bf7\u6c42\u3002\u4e8e\u662f H2 \u6536\u5230\u7b2c 1 \u4e2a\u76f8\u5173\u5e27\uff0c\u76ee\u7684 MAC \u662f\u5168 1 \u5e7f\u64ad\u5730\u5740\u3002<\/p>\n\n\n\n
\u7b2c\u4e8c\u6b65\uff0c\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u6536\u5230 ARP \u8bf7\u6c42\u540e\uff0c\u5411 H1 \u53d1\u9001 ARP \u54cd\u5e94\u3002ARP \u54cd\u5e94\u662f\u5355\u64ad\u5e27\uff1a<\/p>\n\n\n\n
\u6e90 MAC\uff1a00-11-22-33-44-bb\n\u76ee\u7684 MAC\uff1a00-11-22-33-44-cc\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a\u5e27\u4ece S \u7684 1 \u53f7\u7aef\u53e3\u8fdb\u5165\uff0c\u6240\u4ee5 S \u5b66\u4e60\u5230\uff1a<\/p>\n\n\n\n
<00-11-22-33-44-bb, 1>\n<\/code><\/pre>\n\n\n\n
\u540c\u65f6\uff0cS \u5df2\u7ecf\u77e5\u9053 H1 \u7684 MAC \u5728 4 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u8fd9\u4e2a ARP \u54cd\u5e94\u53ea\u4f1a\u88ab\u8f6c\u53d1\u5230 4 \u53f7\u7aef\u53e3\uff0c\u4e0d\u4f1a\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u7b2c\u4e09\u6b65\uff0cH1 \u5df2\u7ecf\u77e5\u9053\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u7684 MAC\uff0c\u4e8e\u662f\u53d1\u9001 DNS \u67e5\u8be2\u3002\u8fd9\u4e2a DNS \u67e5\u8be2\u5e27\u5927\u81f4\u662f\uff1a<\/p>\n\n\n\n
\u6e90 MAC\uff1aH1 \u7684 MAC = 00-11-22-33-44-cc\n\u76ee\u7684 MAC\uff1a\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u7684 MAC = 00-11-22-33-44-bb\n<\/code><\/pre>\n\n\n\n
\u56e0\u4e3a S \u5df2\u7ecf\u77e5\u9053 bb<\/code> \u5728 1 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u8be5\u5e27\u53ea\u8f6c\u53d1\u7ed9 1 \u53f7\u7aef\u53e3\uff0c\u4e0d\u4f1a\u8f6c\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u968f\u540e\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u8fd4\u56de DNS \u54cd\u5e94\uff0c\u544a\u8bc9 H1 www.abc.com<\/code> \u5bf9\u5e94\u7684 Web \u670d\u52a1\u5668 IP \u5730\u5740\u3002\u8fd9\u4e2a\u54cd\u5e94\u5e27\u4ece 1 \u53f7\u7aef\u53e3\u8fdb\u6765\uff0c\u53d1\u5f80 4 \u53f7\u7aef\u53e3\uff0c\u4e5f\u4e0d\u4f1a\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u7b2c\u56db\u6b65\uff0cH1 \u5f97\u5230 Web \u670d\u52a1\u5668 IP \u540e\uff0c\u51c6\u5907\u53d1 HTTP \u8bf7\u6c42\u3002\u56e0\u4e3a Web \u670d\u52a1\u5668\u5728 Internet \u4e0a\uff0c\u4e0d\u5c5e\u4e8e\u672c\u5730\u5b50\u7f51\uff0c\u6240\u4ee5 H1 \u4e0d\u80fd\u76f4\u63a5 ARP Web \u670d\u52a1\u5668\u7684 MAC\uff0c\u800c\u662f\u8981\u628a IP \u6570\u636e\u62a5\u4ea4\u7ed9\u9ed8\u8ba4\u7f51\u5173 R\u3002<\/p>\n\n\n\n
H1 \u6b64\u65f6\u8fd8\u4e0d\u77e5\u9053 R \u5185\u7f51\u63a5\u53e3 192.168.1.1<\/code> \u7684 MAC \u5730\u5740\uff0c\u6240\u4ee5\u8fd8\u8981\u53d1\u9001\u4e00\u6b21 ARP \u8bf7\u6c42\uff1a<\/p>\n\n\n\n
\u8c01\u662f 192.168.1.1\uff1f\u8bf7\u544a\u8bc9 192.168.1.2\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a ARP \u8bf7\u6c42\u540c\u6837\u662f\u5e7f\u64ad\u5e27\uff0c\u76ee\u7684 MAC \u4ecd\u7136\u662f\uff1a<\/p>\n\n\n\n
FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
\u4ea4\u6362\u673a\u4f1a\u628a\u5b83\u6cdb\u6d2a\u5230\u9664 4 \u53f7\u7aef\u53e3\u5916\u7684\u5176\u4ed6\u7aef\u53e3\uff0c\u6240\u4ee5 H2 \u53c8\u4f1a\u6536\u5230\u4e00\u4e2a\u76f8\u5173\u5e27\u3002\u8fd9\u662f H2 \u6536\u5230\u7684\u7b2c 2 \u4e2a\u76f8\u5173\u5e27\u3002<\/p>\n\n\n\n
\u7b2c\u4e94\u6b65\uff0c\u8def\u7531\u5668 R \u6536\u5230 ARP \u8bf7\u6c42\u540e\uff0c\u5411 H1 \u8fd4\u56de ARP \u54cd\u5e94\uff1a<\/p>\n\n\n\n
\u6e90 MAC\uff1a00-11-22-33-44-aa\n\u76ee\u7684 MAC\uff1a00-11-22-33-44-cc\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a\u5e27\u4ece S \u7684 2 \u53f7\u7aef\u53e3\u8fdb\u5165\uff0c\u6240\u4ee5 S \u5b66\u4e60\u5230\uff1a<\/p>\n\n\n\n
<00-11-22-33-44-aa, 2>\n<\/code><\/pre>\n\n\n\n
S \u5df2\u7ecf\u77e5\u9053 H1 \u5728 4 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u8fd9\u4e2a ARP \u54cd\u5e94\u53ea\u53d1\u7ed9 H1\uff0c\u4e0d\u4f1a\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u7b2c\u516d\u6b65\uff0cH1 \u7ec8\u4e8e\u53ef\u4ee5\u53d1\u9001 HTTP \u8bf7\u6c42\u4e86\u3002\u9898\u5e72\u8bf4 t1 \u65f6\u523b S \u7b2c\u4e00\u6b21\u6536\u5230\u5c01\u88c5 HTTP \u8bf7\u6c42\u62a5\u6587\u7684\u4ee5\u592a\u7f51\u5e27\uff0c\u8fd9\u4e2a\u5e27\u4ece H1 \u7684 4 \u53f7\u7aef\u53e3\u8fdb\u5165\uff0c\u76ee\u7684 MAC \u662f\u8def\u7531\u5668 R \u7684 MAC\uff1a<\/p>\n\n\n\n
\u6e90 MAC\uff1a00-11-22-33-44-cc\n\u76ee\u7684 MAC\uff1a00-11-22-33-44-aa\n<\/code><\/pre>\n\n\n\n
\u7531\u4e8e S \u5df2\u7ecf\u77e5\u9053 aa<\/code> \u5728 2 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u8be5 HTTP \u8bf7\u6c42\u5e27\u53ea\u4f1a\u88ab\u8f6c\u53d1\u7ed9\u8def\u7531\u5668 R\uff0c\u4e0d\u4f1a\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u56e0\u6b64 t1 \u65f6\u523b S \u7684\u4ea4\u6362\u8868\u4e2d\u5df2\u7ecf\u5b66\u5230\u4e86 H1\u3001\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u3001\u8def\u7531\u5668 R \u4e09\u4e2a MAC \u5730\u5740\uff1a<\/p>\n\n\n\n
<00-11-22-33-44-cc, 4>\n<00-11-22-33-44-bb, 1>\n<00-11-22-33-44-aa, 2>\n<\/code><\/pre>\n\n\n\n
H2 \u7684 MAC \u5730\u5740\u662f 00-11-22-33-44-dd<\/code>\uff0c\u4f46 H2 \u53ea\u662f\u6536\u5230\u4e86\u5e7f\u64ad\u5e27\uff0c\u6ca1\u6709\u4e3b\u52a8\u53d1\u9001\u5e27\u3002\u4ea4\u6362\u673a\u4e0d\u4f1a\u901a\u8fc7\u201c\u53d1\u51fa\u53bb\u7684\u5e27\u201d\u5b66\u4e60\uff0c\u4e5f\u4e0d\u4f1a\u901a\u8fc7\u201c\u67d0\u53f0\u4e3b\u673a\u6536\u5230\u5e27\u201d\u5b66\u4e60\uff0c\u53ea\u4f1a\u901a\u8fc7\u201c\u6536\u5230\u5e27\u7684\u6e90 MAC \u5730\u5740\u201d\u5b66\u4e60\u3002\u56e0\u6b64\u4ea4\u6362\u8868\u4e2d\u6ca1\u6709\uff1a<\/p>\n\n\n\n
<00-11-22-33-44-dd, 3>\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u8fd9\u9053\u9898\u6700\u5bb9\u6613\u9519\u7684\u5730\u65b9\u6709\u4e09\u4e2a\u3002<\/p>\n\n\n\n
\u7b2c\u4e00\uff0cDNS \u548c ARP \u7684\u89d2\u8272\u4e0d\u80fd\u6df7\u3002DNS \u89e3\u51b3\u7684\u662f\uff1a<\/p>\n\n\n\n
\u57df\u540d \u2192 IP \u5730\u5740\n<\/code><\/pre>\n\n\n\n
ARP \u89e3\u51b3\u7684\u662f\uff1a<\/p>\n\n\n\n
IP \u5730\u5740 \u2192 MAC \u5730\u5740\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5\u8bbf\u95ee www.abc.com<\/code> \u65f6\uff0c\u5148 DNS \u5f97\u5230 Web \u670d\u52a1\u5668 IP\uff1b\u8981\u771f\u6b63\u53d1\u4ee5\u592a\u7f51\u5e27\u65f6\uff0c\u518d\u7528 ARP \u5f97\u5230\u4e0b\u4e00\u8df3 MAC\u3002<\/p>\n\n\n\n
\u7b2c\u4e8c\uff0c\u8bbf\u95ee\u8fdc\u7a0b Web \u670d\u52a1\u5668\u65f6\uff0cH1 \u4e0d\u4f1a\u53bb ARP Web \u670d\u52a1\u5668\u7684 MAC\u3002\u56e0\u4e3a Web \u670d\u52a1\u5668\u5728 Internet \u4e0a\uff0c\u4e0d\u5728\u672c\u5c40\u57df\u7f51\u4e2d\u3002H1 \u53ea\u9700\u8981\u77e5\u9053\u9ed8\u8ba4\u7f51\u5173 R \u7684 MAC \u5730\u5740\u3002<\/p>\n\n\n\n
\u7b2c\u4e09\uff0c\u4ea4\u6362\u673a\u5b66\u4e60\u8868\u9879\u53ea\u770b\u6e90 MAC\uff0c\u4e0d\u770b\u76ee\u7684 MAC\u3002H2 \u6536\u5230\u4e86 ARP \u5e7f\u64ad\u5e27\uff0c\u4f46\u6ca1\u6709\u53d1\u5e27\uff0c\u6240\u4ee5 S \u5b66\u4e0d\u5230 H2 \u7684 MAC \u5730\u5740\u3002<\/p>\n\n\n\n
\u8fd9\u7c7b\u9898\u4ee5\u540e\u53ef\u4ee5\u6309\u4e00\u53e5\u8bdd\u5feb\u901f\u505a\uff1a<\/p>\n\n\n\n
\u5148 DNS \u89e3\u6790\u57df\u540d\uff0c\u518d ARP \u627e\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\uff1b\nDNS \u5f97\u5230\u670d\u52a1\u5668 IP \u540e\uff0c\u518d ARP \u627e\u9ed8\u8ba4\u7f51\u5173\uff1b\n\u4ea4\u6362\u673a\u53ea\u6309\u6e90 MAC \u5b66\u4e60\uff0c\u5e7f\u64ad\u5e27\u4f1a\u5230 H2\uff0c\u5355\u64ad\u5e27\u53ea\u6309\u8868\u8f6c\u53d1\u3002\n<\/code><\/pre>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u90e8\u5206\u662f\u56fe\u4e2d\u5b98\u65b9\u7684\u7ed9\u7ed9\u7684\u56de\u7b54\uff0c\u4f60\u5728\u601d\u8003\u7684\u65f6\u5019\u4e2d\u4f3c\u4e4e\u5c11\u4e86\u4e0d\u5c11\u90e8\u5206\u5185\u5bb9\uff0c\u7279\u522b\u662f\u5173\u4e8ecsma CD\u534f\u8bae\uff0c\u7b2c\u4e8c\u95ee\u8fd8\u662f\u4e0d\u592a\u7406\u89e3\uff0c\u4e0d\u591f\u76f4\u89c2<\/p>\n\n\n\n
\u4f60\u8fd9\u4e2a\u7591\u95ee\u5f88\u5173\u952e\uff1a\u5b98\u65b9\u7b54\u6848\u7b2c\u4e00\u95ee\u628a\u201cCSMA\/CD \u5e27\u201d\u5199\u8fdb\u5c01\u88c5\u94fe\u8def\u91cc\uff0c\u5bb9\u6613\u8ba9\u4eba\u8bef\u4ee5\u4e3a CSMA\/CD \u4e5f\u662f\u50cf UDP\u3001IP \u90a3\u6837\u7684\u4e00\u5c42\u201c\u5c01\u88c5\u534f\u8bae\u201d\u3002\u5b9e\u9645\u4e0a\u5728\u8003\u7814\u8bed\u5883\u4e0b\u8981\u5206\u4e24\u5957\u8bf4\u6cd5\u7406\u89e3\u3002<\/p>\n\n\n\n
\u4e25\u683c\u8bf4\uff0c\u6570\u636e\u94fe\u8def\u5c42\u5c01\u88c5\u7684\u662f\u201c\u4ee5\u592a\u7f51\u5e27\u201d\u6216\u201c\u4ee5\u592a\u7f51 V2 \u5e27\u201d\uff1bCSMA\/CD \u662f\u4f20\u7edf\u5171\u4eab\u5f0f\u4ee5\u592a\u7f51\u7684\u4ecb\u8d28\u8bbf\u95ee\u63a7\u5236\u534f\u8bae\uff0c\u4e0d\u662f\u4e00\u4e2a\u50cf IP\u3001UDP \u90a3\u6837\u627f\u8f7d\u4e0a\u5c42\u6570\u636e\u7684\u7f51\u7edc\u5c42\/\u4f20\u8f93\u5c42\u534f\u8bae\u3002\u5b98\u65b9\u7b54\u6848\u5199\u201cDNS \u62a5\u6587 \u2192 UDP \u6570\u636e\u62a5 \u2192 IP \u6570\u636e\u62a5 \u2192 CSMA\/CD \u5e27\u201d\uff0c\u662f\u6cbf\u7528\u4e86\u65e9\u671f\u6559\u6750\u4e2d\u201c\u4f20\u7edf\u4ee5\u592a\u7f51\u91c7\u7528 CSMA\/CD\uff0c\u56e0\u6b64\u6570\u636e\u94fe\u8def\u5c42\u5e27\u79f0\u4e3a CSMA\/CD \u5e27\u201d\u7684\u8868\u8ff0\u3002\u66f4\u89c4\u8303\u7684\u5199\u6cd5\u5e94\u662f\uff1a<\/p>\n\n\n\n
DNS \u62a5\u6587 \u2192 UDP \u6570\u636e\u62a5 \u2192 IP \u6570\u636e\u62a5 \u2192 \u4ee5\u592a\u7f51 V2 \u5e27\n<\/code><\/pre>\n\n\n\n
\u5982\u679c\u9898\u76ee\u6216\u7b54\u6848\u660e\u663e\u6309\u4f20\u7edf\u4ee5\u592a\u7f51\u6559\u6750\u8868\u8ff0\uff0c\u53ef\u4ee5\u5199\uff1a<\/p>\n\n\n\n
DNS \u62a5\u6587 \u2192 UDP \u6570\u636e\u62a5 \u2192 IP \u6570\u636e\u62a5 \u2192 \u4ee5\u592a\u7f51\u5e27\uff08\u4f20\u7edf\u4ee5\u592a\u7f51\u53ef\u79f0 CSMA\/CD \u5e27\uff09\n<\/code><\/pre>\n\n\n\n
\u8fd9\u6837\u6700\u7a33\u3002\u56e0\u4e3a\u73b0\u4ee3\u4ea4\u6362\u673a\u901a\u5e38\u5de5\u4f5c\u5728\u5168\u53cc\u5de5\u65b9\u5f0f\u4e0b\uff0c\u57fa\u672c\u4e0d\u518d\u4f7f\u7528 CSMA\/CD \u8fdb\u884c\u51b2\u7a81\u68c0\u6d4b\uff1b\u4f46\u662f 408 \u9898\u76ee\u5982\u679c\u6cbf\u7528\u6559\u6750\u672f\u8bed\uff0c\u8fd8\u662f\u4f1a\u628a\u4f20\u7edf\u4ee5\u592a\u7f51\u7684\u6570\u636e\u94fe\u8def\u5c42\u548c CSMA\/CD \u8054\u7cfb\u8d77\u6765\u3002<\/p>\n\n\n\n
\n\n\n\n
\u8fd9\u9898\u7b2c 1 \u95ee\u5b8c\u6574\u601d\u8def\u662f\uff1aH1 \u5728\u6d4f\u89c8\u5668\u91cc\u8f93\u5165 www.abc.com<\/code>\uff0cHTTP \u8bf7\u6c42\u4e0d\u80fd\u76f4\u63a5\u53d1\u51fa\uff0c\u56e0\u4e3a H1 \u8fd8\u4e0d\u77e5\u9053 Web \u670d\u52a1\u5668\u7684 IP \u5730\u5740\u3002\u57df\u540d\u8981\u5148\u89e3\u6790\u6210 IP \u5730\u5740\uff0c\u6240\u4ee5\u9664\u4e86 HTTP\uff0cH1 \u8fd8\u8981\u8fd0\u884c DNS \u5e94\u7528\u5c42\u534f\u8bae\u3002<\/p>\n\n\n\n
DNS \u662f\u5e94\u7528\u5c42\u534f\u8bae\uff0c\u901a\u5e38\u8fd0\u884c\u5728 UDP \u4e4b\u4e0a\uff0c\u6240\u4ee5\u9010\u5c42\u5c01\u88c5\u662f\uff1a<\/p>\n\n\n\n
DNS \u62a5\u6587\n\u2193\nUDP \u6570\u636e\u62a5\n\u2193\nIP \u6570\u636e\u62a5\n\u2193\n\u4ee5\u592a\u7f51 V2 \u5e27\n<\/code><\/pre>\n\n\n\n
\u8fd9\u91cc\u4e0d\u8981\u628a ARP \u6df7\u8fdb\u8fd9\u6761\u5c01\u88c5\u94fe\u3002ARP \u4e5f\u4f1a\u53d1\u751f\uff0c\u4f46 ARP \u7684\u4f5c\u7528\u662f\u201c\u4e3a\u4e86\u53d1\u4ee5\u592a\u7f51\u5e27\uff0c\u5148\u67e5\u8be2\u4e0b\u4e00\u8df3 IP \u5bf9\u5e94\u7684 MAC \u5730\u5740\u201d\u3002ARP \u4e0d\u662f DNS \u62a5\u6587\u7684\u4e0b\u5c42\u5c01\u88c5\uff0cDNS \u62a5\u6587\u4e0d\u4f1a\u88ab ARP \u5c01\u88c5\u3002<\/p>\n\n\n\n
\n\n\n\n
\u7b2c\u4e8c\u95ee\u4e4b\u6240\u4ee5\u4e0d\u76f4\u89c2\uff0c\u662f\u56e0\u4e3a\u5b83\u540c\u65f6\u8003\u4e24\u4e2a\u8868\uff1a<\/p>\n\n\n\n
H1 \u7684 ARP \u8868\uff1a\u8bb0\u5f55 IP \u5730\u5740 \u2192 MAC \u5730\u5740\nS \u7684\u4ea4\u6362\u8868\uff1a\u8bb0\u5f55 MAC \u5730\u5740 \u2192 \u4ea4\u6362\u673a\u7aef\u53e3\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e24\u4e2a\u8868\u7684\u5b66\u4e60\u89c4\u5219\u5b8c\u5168\u4e0d\u540c\u3002<\/p>\n\n\n\n
H1 \u7684 ARP \u8868\u662f\u901a\u8fc7 ARP \u8bf7\u6c42\/\u54cd\u5e94\u5f97\u5230\u7684\u3002\u6bd4\u5982 H1 \u95ee\u201c\u8c01\u662f 192.168.1.126\u201d\uff0c\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u56de\u7b54\u201c\u6211\u662f 192.168.1.126\uff0c\u6211\u7684 MAC \u662f bb\u201d\uff0c\u4e8e\u662f H1 \u8bb0\u5f55 192.168.1.126 \u2192 bb<\/code>\u3002<\/p>\n\n\n\n
\u4ea4\u6362\u673a S \u7684\u4ea4\u6362\u8868\u4e0d\u662f\u9760 ARP \u5185\u5bb9\u5b66\u4e60\uff0c\u800c\u662f\u9760\u201c\u6536\u5230\u7684\u4ee5\u592a\u7f51\u5e27\u7684\u6e90 MAC \u5730\u5740\u201d\u5b66\u4e60\u3002\u4ea4\u6362\u673a\u4ece\u54ea\u4e2a\u7aef\u53e3\u6536\u5230\u67d0\u4e2a\u6e90 MAC \u53d1\u6765\u7684\u5e27\uff0c\u5c31\u8bb0\u4f4f\u8fd9\u4e2a MAC \u5728\u54ea\u4e2a\u7aef\u53e3\u3002<\/p>\n\n\n\n
\u4e5f\u5c31\u662f\uff1a<\/p>\n\n\n\n
ARP \u8868\u770b ARP \u62a5\u6587\u5185\u5bb9\u3002\n\u4ea4\u6362\u8868\u53ea\u770b\u4ee5\u592a\u7f51\u5e27\u7684\u6e90 MAC \u548c\u8fdb\u5165\u7aef\u53e3\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9\u662f\u7b2c\u4e8c\u95ee\u7684\u6838\u5fc3\u3002<\/p>\n\n\n\n
\n\n\n\n
\u5148\u628a\u56fe\u4e2d\u7684\u8bbe\u5907\u548c\u7aef\u53e3\u6574\u7406\u4e00\u4e0b\uff1a<\/p>\n\n\n\n
H1\uff1a\nIP = 192.168.1.2\/25\nMAC = 00-11-22-33-44-cc\n\u8fde\u63a5 S \u7684 4 \u53f7\u7aef\u53e3\n\n\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\uff1a\nIP = 192.168.1.126\/25\nMAC = 00-11-22-33-44-bb\n\u8fde\u63a5 S \u7684 1 \u53f7\u7aef\u53e3\n\n\u8def\u7531\u5668 R \u5185\u7f51\u63a5\u53e3\uff1a\nIP = 192.168.1.1\/25\nMAC = 00-11-22-33-44-aa\n\u8fde\u63a5 S \u7684 2 \u53f7\u7aef\u53e3\n\nH2\uff1a\nIP = 192.168.1.3\/25\nMAC = 00-11-22-33-44-dd\n\u8fde\u63a5 S \u7684 3 \u53f7\u7aef\u53e3\n<\/code><\/pre>\n\n\n\n
\u8fd9\u91cc \/25<\/code> \u7684\u5b50\u7f51\u8303\u56f4\u662f\uff1a<\/p>\n\n\n\n
192.168.1.0 ~ 192.168.1.127\n<\/code><\/pre>\n\n\n\n
\u6240\u4ee5 H1\u3001\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u3001H2\u3001\u8def\u7531\u5668 R \u7684\u5185\u7f51\u63a5\u53e3\u90fd\u5728\u540c\u4e00\u4e2a\u5c40\u57df\u7f51\u91cc\u3002<\/p>\n\n\n\n
\u4f46\u662f www.abc.com<\/code> \u5bf9\u5e94\u7684 Web \u670d\u52a1\u5668\u5728 Internet \u4e0a\uff0c\u4e0d\u5728\u672c\u5c40\u57df\u7f51\u4e2d\u3002\u56e0\u6b64 H1 \u7684\u8bbf\u95ee\u8fc7\u7a0b\u662f\uff1a<\/p>\n\n\n\n
\u5148\u627e\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u505a DNS \u67e5\u8be2\n\u5f97\u5230 Web \u670d\u52a1\u5668 IP \u540e\n\u518d\u628a HTTP \u8bf7\u6c42\u4ea4\u7ed9\u9ed8\u8ba4\u7f51\u5173 R \u8f6c\u53d1\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u73b0\u5728\u4ece t0 \u5f00\u59cb\u4e00\u6b65\u4e00\u6b65\u770b\u3002<\/p>\n\n\n\n
t0 \u65f6\u523b\uff0c\u9898\u76ee\u8bf4 H1 \u7684 ARP \u8868\u4e3a\u7a7a\uff0cS \u7684\u4ea4\u6362\u8868\u4e3a\u7a7a\u3002<\/p>\n\n\n\n
H1 \u60f3\u8bbf\u95ee www.abc.com<\/code>\uff0c\u7b2c\u4e00\u6b65\u8981\u95ee\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u3002H1 \u77e5\u9053\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u7684 IP \u662f 192.168.1.126<\/code>\uff0c\u4f46\u662f\u4e0d\u77e5\u9053\u5b83\u7684 MAC \u5730\u5740\u3002\u56e0\u4e3a H1 \u7684 ARP \u8868\u662f\u7a7a\u7684\uff0c\u6240\u4ee5 H1 \u8981\u5148\u53d1 ARP \u8bf7\u6c42\uff1a<\/p>\n\n\n\n
\u8c01\u662f 192.168.1.126\uff1f\u8bf7\u544a\u8bc9 192.168.1.2\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a ARP \u8bf7\u6c42\u5c01\u88c5\u6210\u4ee5\u592a\u7f51\u5e27\u65f6\uff1a<\/p>\n\n\n\n
\u6e90 MAC = H1 \u7684 MAC = 00-11-22-33-44-cc\n\u76ee\u7684 MAC = FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
\u76ee\u7684 MAC \u662f\u5168 1\uff0c\u56e0\u4e3a ARP \u8bf7\u6c42\u662f\u5e7f\u64ad\u5e27\u3002<\/p>\n\n\n\n
\u8fd9\u4e2a\u5e27\u4ece S \u7684 4 \u53f7\u7aef\u53e3\u8fdb\u5165\u3002\u4ea4\u6362\u673a S \u770b\u5230\u6e90 MAC \u662f cc<\/code>\uff0c\u8fdb\u5165\u7aef\u53e3\u662f 4\uff0c\u4e8e\u662f\u5b66\u4e60\u5230\uff1a<\/p>\n\n\n\n
00-11-22-33-44-cc \u2192 4\n<\/code><\/pre>\n\n\n\n
\u56e0\u4e3a\u8fd9\u4e2a\u5e27\u662f\u5e7f\u64ad\u5e27\uff0c\u6240\u4ee5 S \u4f1a\u628a\u5b83\u4ece\u9664\u4e86 4 \u53f7\u7aef\u53e3\u4ee5\u5916\u7684\u5176\u4ed6\u7aef\u53e3\u90fd\u8f6c\u53d1\u51fa\u53bb\uff0c\u4e5f\u5c31\u662f\u53d1\u7ed9\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u3001R\u3001H2\u3002<\/p>\n\n\n\n
\u6240\u4ee5 H2 \u4f1a\u6536\u5230\u8fd9\u4e2a\u5e27\u3002<\/p>\n\n\n\n
\n\n\n\n
\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u6536\u5230 ARP \u8bf7\u6c42\u540e\uff0c\u53d1\u73b0\u95ee\u7684\u662f\u81ea\u5df1\u7684 IP \u5730\u5740 192.168.1.126<\/code>\uff0c\u4e8e\u662f\u7ed9 H1 \u53d1 ARP \u54cd\u5e94\uff1a<\/p>\n\n\n\n
192.168.1.126 \u7684 MAC \u5730\u5740\u662f 00-11-22-33-44-bb\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a ARP \u54cd\u5e94\u662f\u5355\u64ad\u5e27\uff1a<\/p>\n\n\n\n
\u6e90 MAC = \u672c\u5730\u57df\u540d\u670d\u52a1\u5668 MAC = 00-11-22-33-44-bb\n\u76ee\u7684 MAC = H1 MAC = 00-11-22-33-44-cc\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a\u5e27\u4ece S \u7684 1 \u53f7\u7aef\u53e3\u8fdb\u5165\u3002S \u770b\u5230\u6e90 MAC \u662f bb<\/code>\uff0c\u8fdb\u5165\u7aef\u53e3\u662f 1\uff0c\u4e8e\u662f\u5b66\u4e60\u5230\uff1a<\/p>\n\n\n\n
00-11-22-33-44-bb \u2192 1\n<\/code><\/pre>\n\n\n\n
\u540c\u65f6\uff0cS \u524d\u9762\u5df2\u7ecf\u77e5\u9053 cc<\/code> \u5728 4 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u8fd9\u4e2a ARP \u54cd\u5e94\u53ea\u4f1a\u4ece 4 \u53f7\u7aef\u53e3\u8f6c\u53d1\u7ed9 H1\uff0c\u4e0d\u4f1a\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u5230\u8fd9\u91cc\uff0cS \u7684\u4ea4\u6362\u8868\u5df2\u7ecf\u6709\uff1a<\/p>\n\n\n\n
cc \u2192 4\nbb \u2192 1\n<\/code><\/pre>\n\n\n\n
H1 \u7684 ARP \u8868\u4e5f\u6709\u4e86\uff1a<\/p>\n\n\n\n
192.168.1.126 \u2192 00-11-22-33-44-bb\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u63a5\u4e0b\u6765 H1 \u53ef\u4ee5\u5411\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u53d1\u9001 DNS \u67e5\u8be2\u4e86\u3002\u8fd9\u4e2a DNS \u67e5\u8be2\u5e27\u5927\u81f4\u662f\uff1a<\/p>\n\n\n\n
\u6e90 MAC = H1 MAC = cc\n\u76ee\u7684 MAC = \u672c\u5730\u57df\u540d\u670d\u52a1\u5668 MAC = bb\n<\/code><\/pre>\n\n\n\n
S \u6536\u5230\u8be5\u5e27\u65f6\uff0c\u4f1a\u518d\u6b21\u770b\u5230 cc<\/code> \u4ece 4 \u53f7\u7aef\u53e3\u8fdb\u6765\uff0c\u786e\u8ba4\u6216\u5237\u65b0 cc \u2192 4<\/code>\u3002\u56e0\u4e3a S \u5df2\u7ecf\u77e5\u9053 bb<\/code> \u5728 1 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u8fd9\u4e2a DNS \u67e5\u8be2\u5e27\u53ea\u53d1\u7ed9 1 \u53f7\u7aef\u53e3\uff0c\u4e0d\u4f1a\u5e7f\u64ad\uff0c\u4e5f\u4e0d\u4f1a\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u672c\u5730\u57df\u540d\u670d\u52a1\u5668\u8fd4\u56de DNS \u54cd\u5e94\u65f6\uff1a<\/p>\n\n\n\n
\u6e90 MAC = bb\n\u76ee\u7684 MAC = cc\n<\/code><\/pre>\n\n\n\n
S \u5df2\u7ecf\u77e5\u9053 cc<\/code> \u5728 4 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5 DNS \u54cd\u5e94\u4e5f\u53ea\u53d1\u7ed9 H1\uff0c\u4e0d\u4f1a\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u8fd9\u4e00\u6b65\u5b8c\u6210\u540e\uff0cH1 \u5f97\u5230\u4e86 www.abc.com<\/code> \u5bf9\u5e94\u7684 Web \u670d\u52a1\u5668 IP \u5730\u5740\u3002<\/p>\n\n\n\n
\n\n\n\n
\u7136\u540e H1 \u51c6\u5907\u53d1\u9001 HTTP \u8bf7\u6c42\u3002\u6b64\u65f6 H1 \u4f1a\u5224\u65ad\uff1aWeb \u670d\u52a1\u5668 IP \u662f\u5426\u548c\u81ea\u5df1\u5728\u540c\u4e00\u4e2a\u5b50\u7f51\uff1f<\/p>\n\n\n\n
\u9898\u76ee\u8bf4 Web \u670d\u52a1\u5668\u5728 Internet \u4e0a\uff0c\u6240\u4ee5\u4e0d\u5728\u672c\u5c40\u57df\u7f51\u3002\u65e2\u7136\u76ee\u7684\u4e3b\u673a\u4e0d\u5728\u672c\u5730\u7f51\u7edc\uff0cH1 \u5c31\u4e0d\u4f1a\u53bb\u67e5\u8be2 Web \u670d\u52a1\u5668\u7684 MAC \u5730\u5740\uff0c\u800c\u662f\u8981\u628a IP \u6570\u636e\u62a5\u4ea4\u7ed9\u9ed8\u8ba4\u7f51\u5173\uff0c\u4e5f\u5c31\u662f\u8def\u7531\u5668 R \u7684\u5185\u7f51\u63a5\u53e3 192.168.1.1<\/code>\u3002<\/p>\n\n\n\n
\u4f46\u662f H1 \u7684 ARP \u8868\u91cc\u8fd8\u6ca1\u6709 R \u7684 MAC \u5730\u5740\uff0c\u6240\u4ee5\u8fd8\u8981\u53d1\u7b2c\u4e8c\u6b21 ARP \u8bf7\u6c42\uff1a<\/p>\n\n\n\n
\u8c01\u662f 192.168.1.1\uff1f\u8bf7\u544a\u8bc9 192.168.1.2\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a ARP \u8bf7\u6c42\u4e5f\u662f\u5e7f\u64ad\u5e27\uff1a<\/p>\n\n\n\n
\u6e90 MAC = H1 MAC = 00-11-22-33-44-cc\n\u76ee\u7684 MAC = FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
S \u4ece 4 \u53f7\u7aef\u53e3\u6536\u5230\u8fd9\u4e2a\u5e27\uff0c\u7ee7\u7eed\u786e\u8ba4 cc \u2192 4<\/code>\u3002\u7531\u4e8e\u662f\u5e7f\u64ad\u5e27\uff0cS \u4f1a\u4ece 1\u30012\u30013 \u53f7\u7aef\u53e3\u90fd\u8f6c\u53d1\u51fa\u53bb\uff0c\u6240\u4ee5 H2 \u4f1a\u518d\u6b21\u6536\u5230\u4e00\u4e2a\u4e0e\u672c\u6b21 Web \u8bbf\u95ee\u76f8\u5173\u7684\u5e27\u3002<\/p>\n\n\n\n
\u8fd9\u5c31\u662f\u7b2c 3 \u95ee\u4e2d H2 \u81f3\u5c11\u6536\u5230\u4e24\u4e2a\u5e27\u7684\u6765\u6e90\uff1a\u4e24\u4e2a ARP \u8bf7\u6c42\u5e7f\u64ad\u5e27\u3002<\/p>\n\n\n\n
\n\n\n\n
\u8def\u7531\u5668 R \u6536\u5230 ARP \u8bf7\u6c42\u540e\uff0c\u5411 H1 \u8fd4\u56de ARP \u54cd\u5e94\uff1a<\/p>\n\n\n\n
192.168.1.1 \u7684 MAC \u5730\u5740\u662f 00-11-22-33-44-aa\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9\u4e2a ARP \u54cd\u5e94\u662f\u5355\u64ad\u5e27\uff1a<\/p>\n\n\n\n
\u6e90 MAC = R \u7684 MAC = 00-11-22-33-44-aa\n\u76ee\u7684 MAC = H1 \u7684 MAC = 00-11-22-33-44-cc\n<\/code><\/pre>\n\n\n\n
\u8be5\u5e27\u4ece S \u7684 2 \u53f7\u7aef\u53e3\u8fdb\u5165\u3002S \u770b\u5230\u6e90 MAC \u662f aa<\/code>\uff0c\u8fdb\u5165\u7aef\u53e3\u662f 2\uff0c\u4e8e\u662f\u5b66\u4e60\u5230\uff1a<\/p>\n\n\n\n
00-11-22-33-44-aa \u2192 2\n<\/code><\/pre>\n\n\n\n
S \u5df2\u7ecf\u77e5\u9053 cc<\/code> \u5728 4 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u8fd9\u4e2a ARP \u54cd\u5e94\u53ea\u53d1\u7ed9 H1\uff0c\u4e0d\u53d1\u7ed9 H2\u3002<\/p>\n\n\n\n
\u5230\u8fd9\u91cc\uff0cS \u7684\u4ea4\u6362\u8868\u5df2\u7ecf\u6709\uff1a<\/p>\n\n\n\n
cc \u2192 4\nbb \u2192 1\naa \u2192 2\n<\/code><\/pre>\n\n\n\n
H1 \u7684 ARP \u8868\u91cc\u4e5f\u6709\uff1a<\/p>\n\n\n\n
192.168.1.126 \u2192 bb\n192.168.1.1 \u2192 aa\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u73b0\u5728 H1 \u624d\u80fd\u53d1\u9001\u771f\u6b63\u7684 HTTP \u8bf7\u6c42\u3002\u9898\u76ee\u8bf4 t1 \u65f6\u523b\u662f\u201cS \u7b2c\u4e00\u6b21\u6536\u5230\u5c01\u88c5 HTTP \u8bf7\u6c42\u62a5\u6587\u7684\u4ee5\u592a\u7f51\u5e27\u201d\u3002\u8fd9\u4e2a HTTP \u8bf7\u6c42\u5e27\u662f\u53d1\u5f80 Internet \u7684\uff0c\u6240\u4ee5\u4ee5\u592a\u7f51\u5e27\u7684\u76ee\u7684 MAC \u662f\u9ed8\u8ba4\u7f51\u5173 R \u7684 MAC\uff0c\u800c\u4e0d\u662f Web \u670d\u52a1\u5668\u7684 MAC\u3002<\/p>\n\n\n\n
\u8fd9\u4e2a HTTP \u8bf7\u6c42\u5e27\u5927\u81f4\u662f\uff1a<\/p>\n\n\n\n
\u6e90 MAC = H1 MAC = 00-11-22-33-44-cc\n\u76ee\u7684 MAC = R \u7684 MAC = 00-11-22-33-44-aa\n<\/code><\/pre>\n\n\n\n
\u4ece S \u7684 4 \u53f7\u7aef\u53e3\u8fdb\u5165\u3002S \u5df2\u7ecf\u77e5\u9053 aa<\/code> \u5728 2 \u53f7\u7aef\u53e3\uff0c\u6240\u4ee5\u5b83\u53ea\u628a\u8fd9\u4e2a\u5e27\u8f6c\u53d1\u5230 2 \u53f7\u7aef\u53e3\u7ed9\u8def\u7531\u5668 R\u3002<\/p>\n\n\n\n
\u56e0\u6b64 t1 \u65f6\u523b S \u7684\u4ea4\u6362\u8868\u4e3a\uff1a<\/p>\n\n\n\n
MAC \u5730\u5740                   \u7aef\u53e3\n00-11-22-33-44-cc          4\n00-11-22-33-44-bb          1\n00-11-22-33-44-aa          2\n<\/code><\/pre>\n\n\n\n
\u6ca1\u6709 H2 \u7684\u8868\u9879\uff1a<\/p>\n\n\n\n
00-11-22-33-44-dd \u2192 3\n<\/code><\/pre>\n\n\n\n
\u539f\u56e0\u662f H2 \u867d\u7136\u6536\u5230\u4e86\u5e7f\u64ad\u5e27\uff0c\u4f46 H2 \u6ca1\u6709\u4e3b\u52a8\u53d1\u9001\u5e27\u3002\u4ea4\u6362\u673a\u4e0d\u4f1a\u56e0\u4e3a\u201c\u67d0\u4e2a\u7aef\u53e3\u53d1\u51fa\u53bb\u8fc7\u5e27\u201d\u5c31\u5b66\u4e60\u76ee\u7684\u4e3b\u673a\u7684 MAC\uff0c\u5b83\u53ea\u6839\u636e\u201c\u8fdb\u5165\u4ea4\u6362\u673a\u7684\u5e27\u7684\u6e90 MAC\u201d\u5b66\u4e60\u3002<\/p>\n\n\n\n
\u8fd9\u53e5\u8bdd\u5f88\u91cd\u8981\uff1a<\/p>\n\n\n\n
\u4ea4\u6362\u673a\u5b66\u4e60\u6e90 MAC\uff0c\u4e0d\u5b66\u4e60\u76ee\u7684 MAC\uff1b\u5b66\u4e60\u8fdb\u5165\u7aef\u53e3\uff0c\u4e0d\u5b66\u4e60\u51fa\u53bb\u7aef\u53e3\u3002\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u7b2c 2 \u95ee\u53ef\u4ee5\u7528\u4e00\u4e2a\u8868\u683c\u770b\u5f97\u66f4\u76f4\u89c2\uff1a<\/p>\n\n\n\n
\u6b65\u9aa4<\/th>\u53d1\u751f\u7684\u5e27<\/th>\u6e90 MAC<\/th>\u76ee\u7684 MAC<\/th>\u8fdb\u5165 S \u7684\u7aef\u53e3<\/th>S \u5b66\u5230\u4ec0\u4e48<\/th>\u662f\u5426\u5230 H2<\/th><\/tr><\/thead>
1<\/td>H1 ARP \u67e5\u8be2\u672c\u5730\u57df\u540d\u670d\u52a1\u5668<\/td>cc<\/td>FF-FF-FF-FF-FF-FF<\/td>4<\/td>cc \u2192 4<\/td>\u5230<\/td><\/tr>
2<\/td>\u672c\u5730\u57df\u540d\u670d\u52a1\u5668 ARP \u54cd\u5e94 H1<\/td>bb<\/td>cc<\/td>1<\/td>bb \u2192 1<\/td>\u4e0d\u5230<\/td><\/tr>
3<\/td>H1 \u53d1 DNS \u67e5\u8be2<\/td>cc<\/td>bb<\/td>4<\/td>\u5237\u65b0 cc \u2192 4<\/td>\u4e0d\u5230<\/td><\/tr>
4<\/td>DNS \u670d\u52a1\u5668\u8fd4\u56de DNS \u54cd\u5e94<\/td>bb<\/td>cc<\/td>1<\/td>\u5237\u65b0 bb \u2192 1<\/td>\u4e0d\u5230<\/td><\/tr>
5<\/td>H1 ARP \u67e5\u8be2\u9ed8\u8ba4\u7f51\u5173 R<\/td>cc<\/td>FF-FF-FF-FF-FF-FF<\/td>4<\/td>\u5237\u65b0 cc \u2192 4<\/td>\u5230<\/td><\/tr>
6<\/td>R ARP \u54cd\u5e94 H1<\/td>aa<\/td>cc<\/td>2<\/td>aa \u2192 2<\/td>\u4e0d\u5230<\/td><\/tr>
7<\/td>H1 \u53d1 HTTP \u8bf7\u6c42<\/td>cc<\/td>aa<\/td>4<\/td>\u5237\u65b0 cc \u2192 4<\/td>\u4e0d\u5230<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\u6240\u4ee5\u7b2c 3 \u95ee\u8bf4 H2 \u81f3\u5c11\u6536\u5230\u51e0\u4e2a\u5e27\uff0c\u7b54\u6848\u5c31\u662f\uff1a<\/p>\n\n\n\n
\u81f3\u5c11 2 \u4e2a\u3002\n<\/code><\/pre>\n\n\n\n
\u8fd9 2 \u4e2a\u90fd\u662f ARP \u8bf7\u6c42\u5e7f\u64ad\u5e27\uff0c\u5b83\u4eec\u7684\u76ee\u7684 MAC \u5730\u5740\u90fd\u662f\uff1a<\/p>\n\n\n\n
FF-FF-FF-FF-FF-FF\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u518d\u56de\u5230\u4f60\u63d0\u5230\u7684 CSMA\/CD\u3002\u5b98\u65b9\u7b54\u6848\u7b2c\u4e00\u95ee\u5199\u201c\u6570\u636e\u94fe\u8def\u5c42\u4f7f\u7528 CSMA\/CD \u5e27\u8fdb\u884c\u5c01\u88c5\u201d\uff0c\u8003\u8bd5\u65f6\u8981\u77e5\u9053\u5b83\u60f3\u8868\u8fbe\u7684\u662f\u201c\u5c01\u88c5\u6210\u4f20\u7edf\u4ee5\u592a\u7f51 MAC \u5e27\u201d\u3002\u4f46\u4ece\u4e25\u683c\u6982\u5ff5\u4e0a\u8bf4\uff1a<\/p>\n\n\n\n
\u4ee5\u592a\u7f51\u5e27\uff1a\u5e27\u683c\u5f0f\uff0c\u8d1f\u8d23\u6570\u636e\u94fe\u8def\u5c42\u5c01\u88c5\u3002\nCSMA\/CD\uff1a\u4ecb\u8d28\u8bbf\u95ee\u63a7\u5236\u65b9\u6cd5\uff0c\u8d1f\u8d23\u5171\u4eab\u4ecb\u8d28\u4e0a\u5982\u4f55\u4e89\u7528\u4fe1\u9053\u3001\u68c0\u6d4b\u51b2\u7a81\u3002\n<\/code><\/pre>\n\n\n\n
\u5728\u672c\u9898\u62d3\u6251\u91cc\u6709\u4ea4\u6362\u673a S\u3002\u4ea4\u6362\u673a\u8fde\u63a5\u7684\u4ee5\u592a\u7f51\u901a\u5e38\u53ef\u4ee5\u5de5\u4f5c\u5728\u5168\u53cc\u5de5\u65b9\u5f0f\u4e0b\uff0c\u5168\u53cc\u5de5\u94fe\u8def\u4e0d\u9700\u8981 CSMA\/CD\u3002\u56e0\u6b64\u5b98\u65b9\u4e5f\u63d0\u793a\u201c\u5199\u4ee5\u592a\u7f51 V2 \u5e27\u66f4\u5408\u9002\u201d\u3002\u6240\u4ee5\u540e\u7eed\u505a\u9898\u65f6\u53ef\u4ee5\u8fd9\u6837\u5904\u7406\uff1a<\/p>\n\n\n\n
\u5982\u679c\u9898\u76ee\u95ee\u201c\u9010\u5c42\u5c01\u88c5\u5173\u7cfb\u201d\uff0c\u4f18\u5148\u5199\uff1a<\/p>\n\n\n\n
DNS \u62a5\u6587 \u2192 UDP \u6570\u636e\u62a5 \u2192 IP \u6570\u636e\u62a5 \u2192 \u4ee5\u592a\u7f51 V2 \u5e27\n<\/code><\/pre>\n\n\n\n
\u5982\u679c\u7b54\u6848\u6216\u6559\u6750\u5f3a\u8c03\u4f20\u7edf\u4ee5\u592a\u7f51\uff0c\u5219\u8865\u5145\uff1a<\/p>\n\n\n\n
\u4f20\u7edf\u4ee5\u592a\u7f51\u7684\u6570\u636e\u94fe\u8def\u5c42\u91c7\u7528 CSMA\/CD \u534f\u8bae\u3002\n<\/code><\/pre>\n\n\n\n
\u4e0d\u8981\u628a CSMA\/CD \u7406\u89e3\u6210 DNS \u7684\u4e0b\u4e00\u5c42\u534f\u8bae\u3002\u5b83\u4e0d\u662f\u7f51\u7edc\u5c42\u6216\u4f20\u8f93\u5c42\u534f\u8bae\uff0c\u800c\u662f\u6570\u636e\u94fe\u8def\u5c42 MAC \u5b50\u5c42\u7684\u4ecb\u8d28\u8bbf\u95ee\u63a7\u5236\u673a\u5236\u3002<\/p>\n\n\n\n
\n\n\n\n
\u8fd9\u7c7b\u9898\u4ee5\u540e\u53ef\u4ee5\u6309\u56fa\u5b9a\u5957\u8def\u505a\uff1a<\/p>\n\n\n\n
\u5148\u5224\u65ad\u6709\u6ca1\u6709\u57df\u540d\u3002\u6709\u57df\u540d\uff0c\u5148 DNS\uff1bDNS \u670d\u52a1\u5668\u5728\u672c\u5730\u7f51\u6bb5\uff0c\u5148 ARP DNS \u670d\u52a1\u5668\u3002<\/p>\n\n\n\n
\u518d\u5224\u65ad\u76ee\u6807\u670d\u52a1\u5668\u662f\u5426\u5728\u672c\u5730\u7f51\u6bb5\u3002\u4e0d\u5728\u672c\u5730\u7f51\u6bb5\uff0cHTTP \u8bf7\u6c42\u4ea4\u7ed9\u9ed8\u8ba4\u7f51\u5173\uff1b\u4e0d\u77e5\u9053\u7f51\u5173 MAC\uff0c\u5c31 ARP \u7f51\u5173\u3002<\/p>\n\n\n\n
\u6700\u540e\u66f4\u65b0\u4ea4\u6362\u8868\u65f6\u53ea\u770b\u4e00\u6761\u89c4\u5219\uff1a<\/p>\n\n\n\n
\u4ea4\u6362\u673a\u4ece\u54ea\u4e2a\u7aef\u53e3\u6536\u5230\u5e27\uff0c\u5c31\u628a\u8be5\u5e27\u7684\u6e90 MAC \u8bb0\u5230\u54ea\u4e2a\u7aef\u53e3\u3002\n<\/code><\/pre>\n\n\n\n
H2 \u662f\u5426\u6536\u5230\u5e27\uff0c\u53ea\u770b\u8be5\u5e27\u662f\u4e0d\u662f\u5e7f\u64ad\u5e27\uff0c\u6216\u8005\u4ea4\u6362\u673a\u672a\u77e5\u76ee\u7684 MAC \u65f6\u662f\u5426\u6cdb\u6d2a\u3002\u672c\u9898\u4e2d H2 \u81f3\u5c11\u6536\u5230\u7684\u5c31\u662f\u4e24\u6b21 ARP \u5e7f\u64ad\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u7b2c13\u9898 \u672c\u9898\u8003\u67e5\u7684\u662f\u201cDNS \u67e5\u8be2 RTT + HTTP\/1.1 \u6d41\u6c34\u7ebf\u8bbf\u95ee\u9875\u9762\u5bf9\u8c61\u201d\u7684\u7efc\u5408\u8ba1\u7b97\u3002 \u9898\u5e72\u5173\u952e […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[54],"tags":[],"class_list":["post-2282","post","type-post","status-publish","format-standard","hentry","category-text"],"_links":{"self":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts\/2282","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/comments?post=2282"}],"version-history":[{"count":2,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts\/2282\/revisions"}],"predecessor-version":[{"id":2292,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts\/2282\/revisions\/2292"}],"wp:attachment":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/media?parent=2282"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/categories?post=2282"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/tags?post=2282"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}